Class Size Reduction Research

Class Size Reduction Research

A somewhat shorter version of this bibliography can be downloaded here.

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Smaller classes, higher achievement and narrowing the opportunity gap

Case studies

Benefits for the upper elementary, middle and upper grades

Benefits for post-secondary education

Long-term effects, health and economic benefits

Benefits for teachers and students

Surveys of parents, teachers and students

Non-cognitive skills

Research on the California Class Size Reduction Program (CSRP)

Class size data

Smaller classes, higher achievement and narrowing the opportunity gap 

  • Gilraine, Michael. (2017) Multiple Treatments from a Single Discontinuity: An Application to Class Size.  Also published in the Journal of Labor Economics, Oct. 2020.  As applied to New York City, for the 2008-13 period. “… I show that smaller classes significantly improve student test scores: a four-student decrease in average class size at the school-grade level leads to an improvement of about one-fifth of a standard deviation in math scores and
    around one-seventh of a standard deviation in English scores. These estimates are similar in
    magnitude to those reported by randomized experiments such as Project STAR.”
  • Baker, B. D., Farrie, D. and Sciarra, D. G. (2016), Mind the Gap: 20 Years of Progress and Retrenchment in School Funding and Achievement Gaps. ETS Research Report Series, 2016: 1–37.  “…ample research has indicated that children in smaller classes achieve better outcomes, both academic and otherwise, and that class size reduction can be an effective strategy for closing racially or socioeconomically based achievement gaps .  Although it is certainly plausible that other uses of the same money might be equally or even more effective, there is little evidence to support this … Smaller class sizes and reduced total student loads are a relevant working condition simultaneously influencing teacher recruitment and retention); that is, providing smaller classes may partly offset the need for higher wages for recruiting or retaining teachers.”  The authors’ analysis shows that states with higher teacher/student staffing ratios in higher poverty districts  tend to have lower than expected achievement gaps in Grade 4 and Grade 8 on the NAEPs.
  • Mathis, William J. (2016). Research-Based Options for Education Policymaking: The Effectiveness of Class Size Reduction. National Education Policy Center, University of Colorado. With past research and policy considerations in mind, the brief concludes “class size is an important determinant of student outcomes, and one that can be directly determined by policy.” This is especially crucial for populations which are most effected by large class sizes, such as low-income and minority students. The research brief outlines the benefits of smaller classes in terms of student achievement, graduation rates and non-cognitive skills.  Mathis recommends class sizes between 15-18 (with room for variation based in subject), and argues that while class size reduction can be costly, it could prove to be the most cost-effective policy in the long run.
  • Jacob, Brian, Dynarski, Susan, Libassi, CJ, Crespin, Rene (2016)  Class Size in Michigan: Investigating the Risk of Being in Very Large Classes  An EPI brief. In Michigan, one important predictor of being at risk of being exposed to an especially large class size is race…Black students are, by a considerable margin,the most likely to face class sizes in excess of 40 students. In 9 th grade, a quarter of Black students are in classes of 40 or more, a rate more than twice that of Hispanic students and over 3 times the proportion of white students in such classes….Black students, students attending schools in cities, and students eligible for free or reduced-price lunch at their schools face a disproportionate risk of being in a class of 40 or more. These disparities are particularly troubling because numerous studies have confirmed the negative impact of large classes on test scores and adult outcomes such as college degree completion. Also cautions against using student/teacher ratio as a proxy for class size.
  • Jackson, C. Kirabo., Johnson, Rucker C., Persico, Claudia. (2014) The Effects of School Spending on Educational And Economic Outcomes: Evidence from School Finance Reforms  The Quarterly Journal of Economics. Analyses of school finance reforms reveal that a 10 percent increase in per-pupil spending each year for all twelve years of public schooling leads to 0.31 more completed years of education for students, about 7 percent higher wages, and a 3.2 percentage-point reduction in the annual incidence of adult poverty; with effects more pronounced for children from low-income families. Higher spending increases were associated with notable improvements in measured school inputs, including reductions in student-to-teacher ratios, increases in teacher salaries, and longer school years.
  • Zyngier, David. (2014). Class size and academic results, with a focus on children from culturally, linguistically and economically disenfranchised communities. Evidence Base, issue 1, 2014.  In this research summary, the author examined class size reduction and its effect on student achievement by analyzing 112 peer-reviewed studies, and showed that the overwhelming majority of these studies found that smaller classes have a significant impact on student achievement and narrowing the achievement gap. The author writes, “Noticeably, of the papers included in this review, only three authors supported the notion that smaller class sizes did not produce better outcomes to justify the expenditure.”
  • Schanzenbach, D. W. (2014). Does Class Size Matter? National Education Policy Center Policy Brief. “This policy brief summarizes the academic literature on the impact of class size and finds that class size is an important determinant of a variety of student outcomes, ranging from test scores to broader life outcomes. Smaller classes are particularly effective at raising achievement levels of low-income and minority children.  Policymakers should carefully weigh the efficacy of class-size policy against other potential uses of funds. While lower class size has a demonstrable cost, it may prove the more cost-effective policy overall.”
  • Dynarski, S., Hyman, J., & Schanzenbach, D. W. (2013). Experimental Evidence on the Effect of Childhood Investment on Postsecondary Attainment and Degree Completion. Journal of Policy Analysis and Management 32(4): 692-717.“The study concludes that attending a small class increases the rate of college attendance, with the largest positive impact on black and poor students.  Among those students with the lowest predicted probability of attending college, a small class increased rate of college attendance by 11 percentage points.  Attending a small class also increases the probability of earning a college degree, and to shift students toward earning degrees in high-earning fields such as science, technology, engineering and mathematics (STEM), business and economics.”
  • Achilles, C. M., et al. (2012). Class-size Policy: The Star Experiment and Related Class-size Studies. NCPEA Policy Brief, 1.2. “A reanalysis of the Tennessee STAR experiment found that small classes (15-17 pupils) in kindergarten through third grade (K-3) provide short- and long-term benefits for students, teachers, and society at large….poor, minority, and male students reap extra benefits in terms of improved test outcomes, school engagement, and reduced grade retention and dropout rates.”
  • Shin, Yongyun. (2012). Do Black Children Benefit More From Small Classes? Multivariate Instrumental Variable Estimators With Ignorable Missing Data. Journal of Educational and Behavioral Statistics, 37 (4). An analysis of experimental data from Tennessee’s Student-Teacher  Achievement Ratio study show that, for Black students, reduced class size caused higher academic achievement in the four domains (reading, mathematics, listening, and word recognition skills) each year from kindergarten to third grade, while for other students, it improved the four outcomes except for first-grade listening in kindergarten and first grade only. Evidence shows that Black students benefit more than others from reduced class size in first-, second-, and third-grade academic achievement, substantially narrowing the achievement gap.
  • Bascia, N. (2010). Reducing Class Size: What do we Know?. Ontario Institute for Studies in Education. Analysis of data collected by the Canadian Ministry of Education between 2003-04 and 2007-08  in eight school districts, 24 schools, and 84 classrooms. Classroom observations were undertaken at grades K-3, along with teacher surveys and parent surveys, the latter from every school district in Ontario. “Nearly three-quarters of the primary teachers reported that the quality of their relationships with students had improved as a result of the smaller class size, and two-thirds said their students were more engaged in learning than before class size reduction…Many parents of children enrolled in smaller classes reported that their children appeared to be learning more and were more comfortable at school.”
  • Heilig, J.V., Williams, A. & Jez, S.U. (2010). Input and student achievement: An analysis of Latina/o –serving urban elementary schools. Association of Mexican American Educators (AMAE) Journal, 48 -58. Analysis of data in three of the four largest TX districts (Houston, Dallas and Austin) in 419 schools that were majority Latina/o over 4 years (2005-2008). Evaluated variables such as school funding expenditures, tests scores, ethnicity, and teacher certification, teacher-student ratio and degree obtainment to identify any impact on student achievement in urban elementary schools. “Most powerful predictor of changes in reading and math in all models was decreasing the student teacher ratio…. Essentially, decreasing the student teacher ratio by 1 percentage point would increase the percentage of students proficient on the TAKS by 3% for reading and by 4% for math (p54).”
  • Jepsen, C., & Rivkin, S. (2009). Potential Tradeoff between Teacher Quality and Class Size. Journal of Human Resources, 44.1. This paper investigates the effects of California’s billion-dollar class-size-reduction program on student achievement….”[T]here is little or no support for the hypotheses that the need to hire large numbers of teachers following the adoption of CSR [class-size reduction] led to a lasting reduction in the quality of instruction,” according to the study. “Overall, the findings suggest that CSR increased achievement in the early grades for all demographic groups….”
  • Konstantopoulos, S., & Chun, V. (2009). What Are the Long-Term Effects of Small Classes on the Achievement Gap? Evidence from the Lasting Benefits Study,” American Journal of Education 116.  A summary of the effects of smaller classes on the achievement gap through eighth grade.  Effects significant in all tested subjects, and for students in smaller classes for four years, very substantial. “The results … provided convincing evidence that all types of students (e.g., low, medium, and high achievers) benefit from being in small classes (in early grades) across all achievement tests…. in certain grades, in reading and science, the cumulative effects of small classes for low achievers are substantial in magnitude and significantly different from those for high achievers.  Thus, class size reduction appears to be an intervention that increases the achievement levels for all students while simultaneously reducing the achievement gap.”
  • Babcock, P., & Betts, J.R. (2009). Reduced Class Distinctions: Effort, Ability, and The Education Production Function. Journal of Urban Economics, Vol. 65, pp. 314–322. Empirical findings indicate that class-size expansion may reduce gains for low-effort students more than for high-effort students, Results here…suggest …that larger gains for disadvantaged students may have occurred because small classes allow teachers to incentivize disengaged students more effectively, or because students are better able connect to the school setting in small classes.
  • King, J. B. (2008). Bridging the Achievement Gap: Learning from three charter schools (part 1), (part 2), (part 3), (part 4). Columbia University (Doctoral Dissertation).  “School size and class size are linked to the five key cultural values ….: a culture that teaches effort yields success; a culture of high expectations; a disciplined culture; a culture built on relationships; and a culture of excellence in teaching. Small classes and small overall student loads allow teachers to spend more time working with individual students to help them track their own progress and develop their skills – thus reinforcing the principle that effort yields success. High expectations are easier to maintain when teachers know their students well (because of small school and class size), can identify whether a student’s poor performance on an assessment reflects deficiencies in their effort or their understanding, and can respond accordingly.”
  • Magnuson, K.A., Ruhm, C. & Waldfogel, J. (2007). The persistence of preschool effects: Do subsequent classroom experiences matter? Early Childhood Research Quarterly, 22(1), 18 – 38. Using data from the Early Childhood Longitudinal Study-Kindergarten cohort (ECLS-K), this analysis reveals that children who attended preschool enter public schools with higher levels of academic skills than their peers who experienced other types of child care.  Yet most of the preschool-related gap in academic skills at school entry is quickly eliminated for children placed in small classes and those providing high levels of reading instruction. Conversely, the initial disparities persisted for children experiencing large classes and lower levels of reading instruction.
  • Ready, D. D., & Lee, V. E. (2006/7). Optimal Context Size in Elementary Schools: Disentangling the Effects of Class Size and School Size. Brookings Papers on Education Policy, pp. 99-135. Study finds that class size rather than school size makes a positive difference in elementary schools, and suggests that “if children remained in the same elementary school for five or six years … differences would be very substantial: a roughly 10-point advantage for children in small over large classes by the end of sixth grade, or 4.5 months of additional learning.”
  • Unlu, F. (2005). California Class Size Reduction Reform: New Findings from the NAEP. Princeton University. Study found that California’s fourth grade students who were in reduced class sizes in grades K-3 had substantially higher scores in math on the national assessments (NAEPs), of between 0.2 and 0.3 of a standard deviation, compared to closely matched students who were not in smaller classes.
  • Finn, J. D., et. al. (2005). Small Classes in the Early Grades, Academic Achievement, and Graduating From High School. Journal of Educational Psychology. “For all students combined, 4 years of a small class in K–3 were associated with a significant increase in the likelihood of graduating from high school; the odds of graduating after having attended small classes for 4 years were increased by about 80.0%. Furthermore, the impact of attending a small class was especially noteworthy for students from low-income homes. Three years or more of small classes affected the graduation rates of low-SES students, increasing the odds of graduating by about 67.0% for 3 years and more than doubling the odds for 4 years.”
  • Dee, T. (2004). Teachers, Race, and Student Achievement in a Randomized Experiment. Review of Economics and Statistics. Study showing that student/teacher racial differences appear to negatively effect student achievement in regular size classes. Yet in small classes, students learn more, and racial disparity between teacher and student has no significant effect.
  • Piketty, T. (2004).  Should We Reduce Class Size or School Segregation?  Theory and Evidence from France.  ENS-EHSS, Paris-Jourdan.  Piketty finds that reducing class size in high-poverty schools in France by less than 2 students per class led to a 10% reduction in the achievement gap.  He estimates that reducing class size to 18 students per class in these schools would narrow the achievement gap by 40%, and reducing class size to 15 students per class would eliminate it.
  • Barton, P. (2003). Parsing the Achievement Gap. Educational Testing Service.  Despite the fact that class size reduction has been shown to narrow the achievement gap, this study reveals that schools with large numbers of black and/or limited English students are more likely to have classes of 25 or more.
  • Krueger, A. B., & Whitmore, D. M. (2002). Would Smaller Classes Help Close the Black-White Achievement Gap? from: Bridging the Achievement Gap, Brookings Institution Press. “Our analysis of the STAR experiment indicates that students who attend smaller classes in the early grades tend to have higher test scores while they are enrolled in those grades than their counterparts who attend larger classes….Moreover, black students tend to advance further… from attending a small class than do white students, both while they are in a small class and afterwards. For black students, we also find that being assigned to a small class for an average of two years in grade K – 3 is associated with an increased probability of subsequently taking the ACT or SAT college entrance exam, and 0.15-.20 standard deviation higher average score on the exam.”
  • Fidler, P., Phd. (2002). The Impact of class size reduction on student achievement.  Los Angeles Unified School District, Publication No. 109. “The purpose of this study was to examine the impact of class size reduction (CSR) on achievement among 3rd, 4th, and 5th grade students with different numbers of years of participation in CSR…. We believe that CSR will help to increase student achievement, especially for students who need it the most: low SES students, limited English-speaking students, and those students in inner-city schools…. It can be concluded from the results of this study that CSR does help to increase language achievement gains, especially for ELL students.”
  • Biddle, B., & Berliner, D. (2002).  What Research Says About Small Classes and Their Effects.Wested. “When it is planned thoughtfully and funded adequately, long-term exposure to small classes in the early grades generates substantial advantages for students in American schools, and those extra gains are greater the longer students are exposed to those classes.”
  • McLaughlin, D. and Drori, G. (2000). School-Level Correlates of Academic Achievement: Student Assessment Scores in SASS Public Schools. U.S. Department of Education. National Center for Education Statistics.  The most authoritative study showing the importance of class size is in all grades, analyzing the achievement levels of students in 2,561 schools, as measured by performance on the NAEP (national) exams.  After controlling for student background, the only objective factor found to be positively correlated with student performance was class size, not school size, not teacher qualifications, nor any other variable that the researchers could identify. Student achievement was even more strongly linked to smaller classes in the upper rather than the lower grades.
  • Pritchard, I. (1999). Reducing class size: What do we know? U.S. Department of Education. A comprehensive and wide-scale analysis of CSR analyses, experimental studies and state initiatives. “Researchers have used various techniques to study how class size affects the quality of education.… Overall, however, the pattern of research findings points more and more clearly toward the beneficial effects of reducing class size.
  • Cromwell, S. (1998). Are smaller Classes the Answer? Education World. Thorough analysis of contemporary research articles evincing the benefits of smaller class sizes.
  • Achilles, C. M. (1997). Small Classes, Big Possibilities. The School Administrator. “Perhaps the idea of small classes for students in the early grades is so commonsensical today that educators don’t consider it a challenge. Yet education’s leaders must look beyond the surface variables to understand the systemic, domino-effect possibilities of class-size changes.”
  • National Council of Teachers of English. (1996). Statement on Class Size and Teacher Workload: Elementary. Guideline for NCTE’s position on educational issues is in strong support of smaller class sizes, complete with facts and challenges. All of the major professional organizations in the field of composition recommend course sizes of no more than twenty students for K-1, based on the literature on class size and writing.
  • Mosteller, F. (1995). The Tennessee Study of class size in the early school grades. (1995). The Future of Children, 5.2. Formidable results from the historic large-scale experiment for early grades, Project STAR. “After four years, it was clear that smaller classes did produce substantial improvement in early learning and cognitive studies and that the effect of small class size on the achievement of minority children was initially about double that observed for majority children….”
  • Australian Education Union. Fact Sheet Number 1. (1995). Class sizes do matter.  Fact sheet with evidence from class size research projects and reading list for the general public.
  • Boozer, M., & Rouse, C. (1995). Intraschool variation in class size: patterns and implications. NBER Working Paper, No.5144. “We find that not only are blacks in schools with larger average class sizes, but they are also in larger classes within schools, conditional on class type…it appears that smaller classes at the eighth grade lead to larger test score gains from eighth to tenth grade and that differences in class size can explain approximately 15% of the black-white difference in educational achievement.”
  • Word, Elizabeth et al. (1990) The State Of Tennessee’s Student/Teacher Achievement Ratio (STAR) Project Technical Report Part I and Part II. Database User guide.  Commissioned by the Tennessee State Dept. of Education.  This report contains the results of Tennessee’s ground-breaking 4-year longitudinal randomized class size experiment.   The study analyzed student achievement and development in three class types: small classes with 13-17 students per teacher; regular classes with 22-25 students per teacher, and regular classes with 22-25 students per teacher assisted by a full-time teacher aide. Project STAR followed students from kindergarten through third grade, starting in 1985-1986 and ending in 1988-1989. The study found significant gains in test scores in every subject and every grade, including reading, math, word study and listening, and lower grade retention rates for students who were in smaller classes; but no significant gains for those in classes with an aide.
  • Glass, V. Gene and Mary Lee Smith. (1979). Meta-Analysis of Research on Class Size and Achievement. Early meta-analysis of class size literature. Finds that small class sizes (20 students or less) are associated with improved academic performance. Effects are strongest in the early grades and among low-income students. 

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Case studies

  • Tienken, C.H., & Achilles, C.M. (2006). Making Class Size Work in the Middle Grades. AASA Journal of Scholarship & Practice, 3.1, pp 26-36. In a NJ middle school, reducing class size led to a reduction in the failure rate from 3-6% to only 1%, despite a concurrent increase in 40-60 students, and a 7% increase in poverty students, without any additional spending. Gains in test scores were statistically significant with .80 effect size.
  • O’Neill, J., & Mercier, D. (2003). Incredible Shrinking Class Size. National Staff Development Council.  Describes how one school in Wisconsin reduced class size without additional funding.
  • SERVE. (2002). How Class Size Makes a Difference. One of the best and most readable summaries of the research, prepared by the Regional Educational Laboratory for the Southeast, funded by the U.S. Department of Education. And: “A Parent’s Guide to Class-Size Reduction,” 2003. A useful introduction, including suggestions on actions parents can take to encourage class-size reduction at their schools.
  • Haimson, L. (2000). Smaller is Better: First-hand Reports of Early Grade Class Size Reduction in New York City Public Schools. Education Priorities Panel. This study was carried out during the first year of the class size reduction program for grades K-3 in the New York City public schools. “On the whole, the class size reduction experience as reported by principals and teachers has been overwhelmingly positive….Many of the students placed in smaller classes appear to be learning faster this year….The quality and quantity of teaching have been fundamentally enhanced…noticeable decline in the number of disciplinary referrals among students placed in smaller classes…all of the principals and teachers we interviewed urged that support for the class size program should be continued and expanded.”
  • Class Size: Project SAGE. (n.d.). American Youth Policy Forum. SAGE studies in Wisconsin  began as a five-year pilot program in the 1996-97 school year to test the hypothesis that smaller classes in elementary schools raise the academic achievement of disadvantaged students. SAGE is one of the largest class size reduction initiatives and found significant gains for African American students.

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Benefits for the upper elementary, middle and upper grades

  • Fredriksson, P.,  Öckert, B. & Oosterbeek, H. (2013). Long-Term Effects of Class Size.  The Quarterly Journal of Economics, 128 (1). “Analysis of administrative data from Sweden shows Smaller classes in the last three years of primary school (age 10 to 13) are not only beneficial for cognitive test scores at age 13 but also for non-cognitive scores at that age, for cognitive test scores at ages 16 and 18, and for completed education and wages at age 27 to 42. The estimated effect on wages shows the economic benefits outweigh the costs.”
  • Blatchford, P.,  Bassett, P., & Brown, P. (2011). Examining the effect of class size on classroom engagement and Teacher-pupil interaction- Differences in relation to pupil prior attainment and primary vs. secondary schools. Learning and Instruction, 21. An observational study involving nearly 700 students in 49 schools in the UK finds that in both the early and later grades, smaller classes leads to students receiving more individual attention from their teachers and having more positive interactions with them. Classroom engagement decreases in larger classes, and this is particularly marked for struggling students at the secondary level. Students are engaged in active interactions with their teachers two to three times more often in a class of 15 compared to class of 30, and for low achievers at secondary level there is more than twice as much off task behavior in classes of 30 compared to 15. A five student increase in class size is associated with the odds of off task behavior increasing by 40% for this group. No threshold effect was observed; in other words, there is no particular class size that must be attained for positive benefits to accrue to students in smaller classes.
  •  Malloy, C., Ph.D., & Vital Research, LLC., (2010). Lessons from the Classroom: Initial Success for At-Risk Students. California Teachers Association. “An ongoing evaluation of the Quality Education Investment Act (QEIA) …. This report includes a comparative analysis of Academic Performance Index data for QEIA schools and non-QEIA schools as well as findings from an action research project in 22 QEIA schools statewide… most common goal noted by schools was class size reduction: at least one interviewee at all but one of the regular program schools cited class size reduction as a key goal of QEIA at their school…higher API growth schools cited class size reduction as one of the key factors that contributed to changes in teaching practices at their schools…spend more time with the “neediest, at-risk” students, differentiate instruction, and spend less time on classroom management issue.”
  • Tienken, C.H., & Achilles, C.M. (2006). Making Class Size Work in the Middle Grades. AASA Journal of Scholarship & Practice, 3.1, pp 26-36. In a NJ middle school, reducing class size led to a reduction in the failure rate from 3-6% to only 1%, despite a concurrent increase in 40-60 students, and a 7% increase in poverty students, without any additional spending. Gains in test scores were statistically significant with .80 effect size.
  • Dustmann, C., et. al. (2003). Class Size, Education and Wages. Economic Journal. UK study showing high school students in small classes more likely to stay through graduation. See also Guardian UK summary. Explanation of the previous analysis’ findings.
  • McLaughlin, Donald and Gili Drori.(2000) School-Level Correlates of Academic Achievement: Student Assessment Scores in SASS Public Schools. U.S. Department of Education. National Center for Education Statistics. The most authoritative study showing the importance of class size is in all grades, analyzing the achievement levels of students in 2,561 schools, as measured by performance on the NAEP (national) exams.  After controlling for student background, the only objective factor found to be positively correlated with student performance was class size, not school size, not teacher qualifications, nor any other variable that the researchers could identify. Student achievement was even more strongly linked to smaller classes in the upper rather than the lower grades.
  • National Council of Teachers of English. (1999). More than a Number: Why Class Size Matters. Guideline for NCTE’s position on educational issues is in strong support of smaller class sizes, complete with facts and challenges.
  • Wenglinsky, H.(1997).  When Money Matters. Educational Testing Service. Shows how smaller classes in grades 4 and 8 are linked to higher test scores and improved student discipline.
  • Boozer, M.,  & Rouse, C. (1995). Intraschool variation in class size: patterns and implications. NBER Working Paper, No. 5144.“We find that not only are blacks in schools with larger average class sizes, but they are also in larger classes within schools, conditional on class type…it appears that smaller classes at the eighth grade lead to larger test score gains from eighth to tenth grade and that differences in class size can explain approximately 15% of the black-white difference in educational achievement.”
  • National Council of Teachers of English. (1990). Statement on Class Size and Teacher Workload: Secondary. “The Secondary Section of the National Council of Teachers of English recommends that schools, districts, and states adopt plans and implement activities resulting in class sizes of not more than 20 and a workload of not more than 80 for English language arts teachers by the year 2000.”

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Benefits for post-secondary education

  • Benton, S. (2012). Does Class Size Matter? The IDEA Center Blog. Analyses of IDEA student ratings collected in 490,196 classes from 2002-2011 found, “…Small classes…better student preparation, student enthusiasm, and effort than those in large and very large classes…the smaller the class the higher was students’ achievement and overall impressions of the course…. Smaller classes were especially well suited for developing students’ creative capacities and oral and written communication skills.”
  • Monks, J., & Schmidt, R. (2010). The impact of class size and number of students on outcomes in higher education. Working Paper, Cornell University, School of Industrial and Labor Relations. “We find that both class size and student load negatively impact student assessments of courses and instructors… large class sizes and higher student loads are correlated with less critical and analytical thinking, less clarity in class presentations, and lower ratings on the instructor’s ability to stimulate student interest.”
  • De Giorgi, G., Pellizzari, M., & Woolston, W. G. (2009). Class size and class heterogeneity. IZA Discussion Papers, No. 4443. “Our baseline results suggest that increasing class size by 20 students reduces a student’s wage by approximately 6%. If we trust such estimate, it would be hard to dismiss class size reduction as an ineffective and inefficient policy….Such an intervention [reducing average class sizes to 20 students] would generate a gain of 80 euros x 1,500 students, or 120,000 euros in total each month, which are likely to be more than enough to pay the costs of acquiring the additional resources necessary to activate the two extra classes.”
  • Cuseo, J. (2007). The empirical case against large class size: Adverse effects on the teaching, learning, and retention of first-year students. Journal of Faculty Development, 21(1), p5-21. “Good summary showing  that “empirical evidence…suggests that there are eight deleterious outcomes associated with large-sized classes: (1) increased faculty reliance on the lecture method of instruction, (2) less active student involvement in the learning process, (3) reduced frequency of instructor interaction with and feedback to students, (4) reduced depth of student thinking inside the classroom, (5) reduced breadth and depth of course objectives, course assignments, and course-related learning strategies used by students outside the classroom, (6) lower levels of academic achievement (learning) and academic performance (grades), (7) reduced overall course satisfaction with the learning experience, and (8) lower student ratings (evaluations) of course instruction.”
  • Beddard, K., & Kuhn, P. (2005). Where class size really matters: Class size and student ratings of instructor effectiveness. Working Paper. University of California, Santa Barbara: Department of Economics. The researchers examined the impact of class size on student evaluations of instructor performance using data on all economics classes offered at the University of California, Santa Barbara from Fall 1997 to Spring 2004. The researchers controlled for both instructor and course fixed effects. The researchers found a large, highly significant, and nonlinear negative impact of class size on student evaluations of instructor effectiveness that is highly robust to the inclusion of course and instructor fixed effects.
    • Keil, J. and Partell, P. J. (1997) The effect of class size on student performance and retention at Binghamton University. Office of Budget and Institutional Research, Binghamton University. A study of Binghamton students, with an accounting for demographic variables. Increasing class size had a negative effect on student achievement and retention. A student with an average class size of 20 had a 0.97 probability of returning to the university, whereas a student with an average class size of 240 had a probability of returning of only 0.80.
    • Horning, A. (1997). The Definitive article on class size. WPA: Writing Program Administration, 31.1/2. Compilation of class size research evincing CSR’s beneficial impact on first-year college students’ writing courses leading to improved college ranking, faculty effectiveness and school’s retention rate,“It should be clear that class size is important from a number of different perspectives in college writing courses. For students, … how much attention they get from teachers, how deeply they engage with their coursework and how well they can develop their writing skills. Ultimately, these differences make a difference in their performance and persistence to degree completion…. While cost is important to institutions, it must be viewed from a big picture point of view.”
    • Kuh, G. D., et al. (1991). Involving colleges: Successful approaches to fostering student learning and personal development outside the classroom. San Francisco: Jossey-Bass. In a multi-campus observation-based study, the researchers found that large classes were the primary factor in students not engaging in courses. In very large courses the majority of students did not have a single interaction with the professor.
    • NCTE: National Council of Teachers of English. (1987). Statement on Class Size and Teacher Workload: College. “Economic pressures and budgetary restrictions may tempt administrations to increase teaching loads. With this conflict in mind, the College Section of the National Council of Teachers of English endorses the following standards….No more than 20 students should be permitted in any writing class. Ideally, classes should be limited to 15. Students cannot learn to write without writing. In sections larger than 20, teachers cannot possibly give student writing the immediate and individual response necessary for growth and improvement.”
  • Fischer, C. G., & Grant, G. E. (1983). Intellectual levels in college classrooms. In C. L. Ellner, & C. P. Barnes (Eds.), Studies of college teaching: Experimental results. Lexington, Mass.: D.C. Heath. In an analysis of audiotapes of 155 class sessions in 40 undergraduate courses at multiple institutions, the researchers found that class size significantly affected the level of cognitive skills used by students in the classroom. In small classes (15 or fewer students), when students spoke in response to instructor-posed questions, the average level of thinking displayed by their discourse was that of analysis; in medium-size classes (16-45 students) student discourse was characterized by a lower level of thinking—comprehension; and in large classes (46 or more students), the discourse of students who participated in class most often reflected factual recall.

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Long-term effects, health and economic benefits

  • Dynarski, S., Hyman, J., &  Schanzenbach, D. W. (2011). Experimental Evidence on the Effect of Childhood Investment on Postsecondary Attainment and Degree Completion. NBER, Working Paper.  “The study concludes that attending a small class increases the rate of college attendance, with the largest positive impact on black and poor students.  Among those students with the lowest predicted probability of attending college, a small class increased rate of college attendance by 11 percentage points.  Attending a small class also increases the probability of earning a college degree, and to shift students toward earning degrees in high-earning fields such as science, technology, engineering and mathematics (STEM), business and economics.”
  • Fredriksson, P.,  Öckert, B. & Oosterbeek, H. (2013). Long-Term Effects of Class Size.  The Quarterly Journal of Economics, 128 (1). Analysis of administrative data from Sweden shows Smaller classes in the last three years of primary school (age 10 to 13) are not only beneficial for cognitive test scores at age 13 but also for non-cognitive scores at that age, for cognitive test scores at ages 16 and 18, and for completed education and wages at age 27 to 42. The estimated effect on wages shows the economic benefits outweigh the costs.
  • Chetty, R.,  et. al. (2011). How Does your Kindergarten classroom affect your earnings? Evidence from Project Star. The Quarterly Journal of Economics, 126:4. Smaller classes in Kindergarten shown to lead to greater likelihood of attending college, owning a home and a 4101K as adults more than 20 years later.
  • Dee, T., & West, M. (2011). The Non-Cognitive Returns to Class Size. Educational Evaluation and Policy Analysis, 33:23.  “Results show that smaller classes in 8th grade lead to improvements in non-cognitive skills like student engagement, persistence and self-esteem that have been strongly linked to success in schools and later in life. The authors estimate that in urban schools, the economic benefits from investing in smaller classes would be nearly twice the cost.”
  • De Giorgi, G., Pellizzari, M., & Woolston, W. G.  (2009). Class size and class heterogeneity.  IZA Discussion Papers, No. 4443. “Our baseline results suggest that increasing class size by 20 students reduces a student’s wage by approximately 6%. If we trust such estimate, it would be hard to dismiss class size reduction as an ineffective and inefficient policy….Such an intervention [reducing average class sizes to 20 students] would generate a gain of 80 euros x 1,500 students, or 120,000 euros in total each month, which are likely to be more than enough to pay the costs of acquiring the additional resources necessary to activate the two extra classes.”
  • Muennig, P., & Woolf, S. H. (2007). Health and Economic Benefits of Reducing the Number of Students per Classroom in US Primary Schools. American Journal of Public Health. “Reducing class sizes may be more cost-effective than most public health and medical interventions, with large savings in health care costs and almost two years of additional life for students who were in smaller classes in the early grades.” See also 2007 summary in Slate magazine by Dr. Sydney Spiesel.
  • Yinger, John (2007).  The Impact of Class Size on Teacher Retention.  The findings that smaller classes lower teacher attrition rates “may be particularly important for schools with high concentrations of disadvantaged students, which have relatively high rates of teacher attrition. Existing research indicates that these schools would have to offer huge salary increases to bring their attrition rates down to the level in schools with few disadvantaged students. As a result, policies to reduce class size may, in the long run, prove to be more cost effective than salary increases as a way to retain teachers and boost teacher experience in schools with concentrated disadvantage.”
  • Finn, J. D., et. al. (2005). Small Classes in the Early Grades, Academic Achievement, and Graduating From High School. Journal of Educational Psychology. “For all students combined, 4 years of a small class in K–3 were associated with a significant increase in the likelihood of graduating from high school; the odds of graduating after having attended small classes for 4 years were increased by about 80.0%. Furthermore, the impact of attending a small class was especially noteworthy for students from low-income homes. Three years or more of small classes affected the graduation rates of low-SES students, increasing the odds of graduating by about 67.0% for 3 years and more than doubling the odds for 4 years.”
  • Dustmann, C.,  et. al. (2003). Class Size, Education and Wages. The Economic Journal. UK study showing high school students in small classes more likely to stay through graduation. See also Guardian UK summary. Explanation of the previous analysis’ findings.
  • Krueger, A. K. (2003). Economic Considerations and Class Size. The Economic Journal, 113.  Concludes that “the benefits of reducing class size are
    estimated to be around twice the cost.”  Also includes an authoritative critique of Hanushek’s work: “Hanushek’s pessimistic conclusion about the effectiveness of schooling inputs results from the fact that he inadvertently places a disproportionate share of weight on a small number of studies that frequently used small samples and estimated misspecified models.”
  • Viadero, D. (2000). Study Links Smaller Classes To Higher Earnings. Education Week. Summary of Krueger’s economic analysis.

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Benefits for teachers and students

  • Achilles, C. M., et al. (2012). Class-size Policy: The Star Experiment and Related Class-size Studies. NCPEA Policy Brief 1.2. “A reanalysis of the Tennessee STAR experiment found that small classes (15-17 pupils) in kindergarten through third grade (K-3) provide short- and long-term benefits for students, teachers, and society at large….poor, minority, and male students reap extra benefits in terms of improved test outcomes, school engagement, and reduced grade retention and dropout rates.”
  • Isenberg, Emily Pas. (2010). US Bureau of the Census. The Effect of Class Size on Teacher Attrition: Evidence from Class Size Reduction Policies in New York State.  A decrease in class size from 23 to 20 students  under a district-wide policy lowered the probability that a teacher would leave the school by 4.2 percentage points.  By decreasing teacher turnover rates which then leads to a more effective experienced teaching force, class size reduction can “improve student achievement through both the direct effect of smaller classes on student achievement and the indirect effects of decreasing the fraction of beginning teachers in the classroom and decreasing the disruption associated with teacher turnover.”
  • Bascia, N. (2010). Reducing Class Size: What do we Know?. Ontario Institute for Studies in Education. Reviewed research base and analyzed statistical data collected by the Canadian Ministry of Education between 2003-04 and 2007-08. Involved field research in eight school districts, 24 schools, and 84 classrooms. Classroom observations were undertaken at each primary grade level, from K-3. All teachers were surveyed in each school. Parent surveys included representation from every school district in Ontario. “Nearly three-quarters of the primary teachers reported that the quality of their relationships with students had improved as a result of the smaller class size, and two-thirds said their students were more engaged in learning than before class size reduction…Many parents of children enrolled in smaller classes reported that their children appeared to be learning more and were more comfortable at school.”
  • King, J. (2008). Bridging the Achievement Gap: Learning from three charter schools (part 1), (part 2), (part 3), (part 4). Columbia University (Doctoral Dissertation). “School size and class size are linked to the five key cultural values ….: a culture that teaches effort yields success; a culture of high expectations; a disciplined culture; a culture built on relationships; and a culture of excellence in teaching. Small classes and small overall student loads allow teachers to spend more time working with individual students to help them track their own progress and develop their skills – thus reinforcing the principle that effort yields success. High expectations are easier to maintain when teachers know their students well (because of small school and class size), can identify whether a student’s poor performance on an assessment reflects deficiencies in their effort or their understanding, and can respond accordingly.”
  • Graue,E.,  et. al. (2007). The Wisdom of Class-Size Reduction. American Educational Research Journal, 44.3.  “SAGE in particular, and CSR in general, allows teachers the space to create meaningful learning opportunities for students. Giving teachers support to develop new strategies for teaching smaller groups makes it more likely.”
  • Wilson, V. (2002). Does Small Really Make a Difference? University of Glasgow . Good literature review on the effects of class size on teaching and student behavior.
  • Finn, J.., Pannozzo, Gina M., and Achilles, Charles M. (2003) The Why’s of Class Size: Student Behavior in Small Classes, Review of Educational Research, Vol. 73, No. 3, pp. 321-368. This article summarizes theory and data on [the] hypothesis- that the key to the academic benefits of small classes resides in student behavior. ..students become more engaged academically and more engaged socially when class sizes are reduced, and this increased engagement in the classroom is a compelling explanation for increased learning in all subject areas.

  • Fidler, P., Phd. (2002). The Relationship between teacher instructional techniques and characteristics and student achievement in reduced size classes. Los Angeles Unified School District, Publication No. 120. “The purpose of this study was to examine the impact of class size reduction (CSR) on achievement among 3rd, 4th, and 5th grade students with different numbers of years of participation in CSR…. We believe that CSR will help to increase student achievement, especially for students who need it the most: low SES students, limited English-speaking students, and those students in inner-city schools…. It can be concluded from the results of this study that CSR does help to increase language.”
  • Bernstein, K. J. (2000). Class size does matter. Prince George’s and Montgomery Journal Newspapers.  Excellent essay by a high school teacher, explaining why both smaller classes and a smaller teaching load is essential to improve student achievement.

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Surveys of parents, teachers and students

  • Launch Michigan 2019 survey of 6,878 Michigan educators by Emma White Research LLC. Educators believe that reducing class size would be the best way to improve schools a 80%, with 85% of teachers in high-poverty urban districts responding this way, far above either expanding preK or providing more literacy coaches.  Teachers with large classes were also more likely to say they want to leave the profession.

 

 

 

 

 

 

 

  • Colorado Education Association (2018) Teacher Voices: Teachers Know what their Schools and Students Need.  A statewide survey of  742 educators  shows that 74% of teachers statewide say that schools need to reduce class sizes to allow for one-on-one attention”, the top response of the nine options offered. Mesa County teacher Christy Anderson, an educator for 19 years, wrote: “Anyone who says that class size doesn’t matter,” she explains, “does not understand teaching.”

 

 

 

  • New York Teacher (2014)  What works, what doesn’t: Teachers speak their minds.  A survey of NYC teachers found that 99 percent say reducing class size would be the most effective reform to improve student outcomes – far outstripping any other reform, including socio-emotional learning, universal preK, community schools, and college-reading standards.  Ninety one percent said it would be a very effective reform, and another 8 percent rated it somewhat effective.

 

 

 

 

  • The Friedman Foundation for Educational Choice. (2014). School Choice Signals, Research Review and Experiments. A national survey of more than 50,000 people as part of the 2012 post-election phase of the Congressional Election Study (CCES), administered by  YouGov/Polimetrix indicated that respondents perceived that the most effective way to reform education in the U.S. is to reduce class sizes, ahead of technology or school choice.

 

  • New York City Department of Education. (2012). School Survey Citywide Results. NYC DOE Learning Environment Surveys. Smaller classes are the top priority of parents every year since they’ve been given (2009).  See also p. 9 summary slides at School Survey Citywide Results(2011).
  • Teach Plus. (2012). Great Expectations: Teachers’ Views on Elevating the Teaching Profession. Survey. “Just 4 percent of veteran teachers and 6 percent of New Majority teachers would be willing to increase class sizes in exchange for a higher salary. Slightly over half of teachers at all levels of experience suggest raising taxes as their preferred strategy for paying for larger salaries, indicating disinterest in trading off class size, a longer year, or a new pension system to pay for the potential increase.”
  • Scholastic & Bill and Melinda Gates Foundation. (2012.) Primary Sources: America’s Teachers on the Teaching Profession. 90 percent of teachers said that having fewer students in their class would have a “very strong” (62 percent) or “strong” impact (28 percent) on student achievement, while only 26 percent said that merit pay would have a strong and/or very strong impact.
  • MetLife, Inc.. (2012). The MetLife Survey of the American Teacher: Teachers, Parents and the Economy. A 2011 survey of teachers, parents and students. “Teacher job satisfaction has dropped 15 points since 2009, from 59% who were very satisfied to 44% who are very satisfied, the lowest level in over 20 years….Teachers with lower job satisfaction are more likely to report that in the last year they have seen increases in: average class size (70% vs. 53%)…One in seven (14%) students agrees that their classes are so big that their teachers don’t really know them….”
  • Education Next-Program on Education Policy and Governance. (2007-11). Education Next-PEPG Survey. This poll of the American public found that 77 percent of respondents thought that additional educational dollars should be spent on smaller classes rather than higher teacher salaries.
  • Lopez, S. J., Ph.D.(2009). Well-Being, Success, and the Gallup Student Poll. Gallup, Inc.. The larger the class size, the lower the sense of student well being.
  • New South Wales.(2004-08).  Evaluations of class size reduction program. “Overwhelmingly the judgment of parents, principals and teachers has been that the impact of the Class Size Reduction Program has been positive. It has been exceptionally well regarded by these groups as an important educational initiative. High levels of satisfaction were reported with the program’s impact on class organization, teaching practices, student learning outcomes, behavior and social skills.”
  • Bridgeland, J. M., et. al. (2006). The Silent Epidemic: Perspectives of High School Dropouts. National survey of high school dropouts: “In our focus groups, participants repeated again and again that they believed smaller class sizes would have helped ensure that teachers maintained order in the classroom and would have provided more individual attention. …the need for smaller class sizes and more personal instruction emerged more than 12 separate times from the participants in our four focus groups…Seventy-five percent of survey participants say that if they had had been provided with smaller classes they would likely have stayed in school.”
  • Beddard, K., & Kuhn, P. (2005). Where class size really matters: Class size and student ratings of instructor effectiveness. Working Paper. University of California, Santa Barbara: Department of Economics. The researchers examined the impact of class size on student evaluations of instructor performance using data on all economics classes offered at the University of California, Santa Barbara from Fall 1997 to Spring 2004. The researchers controlled for both instructor and course fixed effects. The researchers found a large, highly significant, and nonlinear negative impact of class size on student evaluations of instructor effectiveness that is highly robust to the inclusion of course and instructor fixed effects.
  • New York City Council Investigation Division. (2004).  Report on Teacher Attrition and Retention. “Nearly a third (30%) of new teachers (1-5 years of experience) in NYC said that it was unlikely that they would be teaching school in the next three years.  For those teachers who were thinking of leaving NYC public schools, the top three changes in their work conditions most likely to entice them to stay include a new contract with higher pay; class size reduction; and better discipline”
  • Public Agenda. (2003).Rolling Up Their Sleeves: Superintendents and Principals Talk About What’s Needed to Fix Public Schools. “Superintendents and Principals agree that reducing class size would significantly improve quality of teaching, with principals saying it would be the best way (at 36%), over higher salaries (35%) or merit pay (25%).”
  • Public Agenda. (2001). Sizing Things Up. ” 70% of teachers say that small classes are more important to student achievement than small school size. Parents: 47% say class size more important,  only 8% school size, and 43% say both.   In focus groups across the country, Public Agenda has repeatedly heard parents and teachers talk about how students benefit from – and thrive—in small classes.”
  • Public Agenda. (1999). A Sense of Calling: Who Teaches and Why.  “86% of teachers say that reducing class size would be a very effective way to improve the quality of instruction, far above any other reform, including requiring a major in the subject taught, increasing professional development or salaries, providing more mentoring, requiring graduate degrees, or merit pay.”
  • Carbone, E., & Greenberg, J. (1998). Teaching large classes: Unpacking the problem and responding creatively. To Improve the Academy. Paper 399.  The researchers found that most students agreed that class size affected their ability to learn, and large classes negatively affected their ability to interact  (in and out of class) with faculty.
  • Fischer, C. G., & Grant, G. E. (1983). Intellectual levels in college classrooms. In C. L. Ellner, & C. P. Barnes (Eds.), Studies of college teaching: Experimental results. Lexington, Mass.: D.C. Heath. In an analysis of audiotapes of 155 class sessions in 40 undergraduate courses at multiple institutions, the researchers found that class size significantly affected the level of cognitive skills used by students in the classroom. In small classes (15 or fewer students), when students spoke in response to instructor-posed questions, the average level of thinking displayed by their discourse was that of analysis; in medium-size classes (16-45 students) student discourse was characterized by a lower level of thinking—comprehension; and in large classes (46 or more students), the discourse of students who participated in class most often reflected factual recall.

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Non-cognitive skills

  • Fredriksson, P., Öckert, B. & Oosterbeek, H. (2011). Long-Term Effects of Class Size.  IZA Discussion Paper # 5879. “Analysis of administrative data from Sweden shows Smaller classes in the last three years of primary school (age 10 to 13) are not only beneficial for cognitive test scores at age 13 but also for non-cognitive scores at that age, for cognitive test scores at ages 16 and 18, and for completed education and wages at age 27 to 42. The estimated effect on wages shows the economic benefits outweigh the costs.”
  • Dee, T. & West, M. (2011). The Non-Cognitive Returns to Class Size. Educational Evaluation and Policy Analysis, 33:23. Results show that smaller classes in 8th grade lead to improvements in non-cognitive skills like student engagement, persistence and self-esteem that have been strongly linked to success in schools and later in life. The authors estimate that in urban schools, the economic benefits from investing in smaller classes would be nearly twice the cost.
  • Babcock, P., & Betts, J.R. (2009). Reduced Class Distinctions: Effort, Ability, and The Education Production Function. Journal of Urban Economics, Vol. 65, pp. 314–322. Empirical findings indicate that class-size expansion may reduce gains for low-effort students more than for high-effort students, Results here…suggest …that larger gains for disadvantaged students may have occurred because small classes allow teachers to incentivize disengaged students more effectively, or because students are better able connect to the school setting in small classes.
  • Blatchford, P., et.al. (2008). Do low attaining and younger students benefit most from small classes? Results from a systematic observation study of class size effects on pupil classroom engagement and teacher pupil interaction. Paper delivered to the American Educational Research Association Annual Meeting. “…[T]he main implication of this study is that smaller classes can benefit all pupils in terms of individual, active attention from teachers, but that the lower attaining pupils in particular can benefit from small classes at secondary level.”

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Research on the California Class Size Reduction Program (CSRP)

  • Gilraine M., Macartney H., and McMillan, R. Education Reform in General Equilibrium: Evidence from California’s Class Size Reduction. NBER Working Paper No. 24191, January 2018. An analysis of California’s statewide class size reduction  of the late-1990’s shows that improvements in public school quality caused marked reductions in local private school enrollment as higher-income students enrolled in public schools, and also led to significant increases in local house prices, as parents were parents were willing to pay substantially more to live in a region that had implemented class size reduction. Second, the authors found a large pure class size achievement effect of 0.11 SD (in terms of mathematics scores), and an even larger indirect effect of 0.16 SD via induced changes in school demographics and peer effects. Finally, both effects persisted positively, giving rise to an impact estimated to be 0.4 SD higher for fourth graders who were in reduce size classes for four years from Kindergarten through third grade. Re teacher quality: ” …once the CSR program expands to kindergarten and third grade: teacher inexperience falls substantially for CSR grades and rises for non-CSR grades. Inexperience then falls for all grades thereafter.” Conclusion:  “…our  results  accord  with  the  convincing  studies  that  document  longer-term  benefits  of  class  size  reduction.”
  • Burkander, P. (2014). The Causal Effect of School Reform: Evidence from California’s Quality Education Investment Act*. “This report analyzes the California Quality Education Investment Act (QEIA) that went into effect in 2007-08 and its effect on student outcomes.  In his analysis, the author finds that QEIA led to a reduction in class size of about four students by the third fully-funded year of the program. QEIA caused a statistically significant increase in student achievement, as measured by both California’s Average Performance Index, and by grade-level results on standardized tests. With respect to the population of all elementary schools, the average treatment effect of QEIA on the API by the third fully-funded year of the program was an increase of 0.33 standard deviations, with larger gains for Hispanic and low-SES students. Standardized math scores increased 0.28 standard deviations in 2nd grade, and by 0.44 standard deviations in 5th grade. QEIA caused more modest gains in English language arts, of 0.19 and 0.22 standard deviations in 2nd and 5th grade, respectively.“
  • Malloy, C., Ph.D., & Vital Research, LLC., (2010). Lessons from the Classroom: Initial Success for At-Risk Students. California Teachers Association. “An ongoing evaluation of the Quality Education Investment Act (QEIA) …. This report includes a comparative analysis of Academic Performance Index data for QEIA schools and non-QEIA schools as well as findings from an action research project in 22 QEIA schools statewide… most common goal noted by schools was class size reduction: at least one interviewee at all but one of the regular program schools cited class size reduction as a key goal of QEIA at their school…higher API growth schools cited class size reduction as one of the key factors that contributed to changes in teaching practices at their schools…spend more time with the “neediest, at-risk” students, differentiate instruction, and spend less time on classroom management issue.”
  • Unlu, F. (2005). California Class Size Reduction Reform: New Findings from the NAEP. Princeton University. Study found that California’s fourth grade students who were in reduced class sizes in grades K-3 had substantially higher scores in math on the national assessments (NAEPs), of between 0.2 and 0.3 of a standard deviation, compared to closely matched students who were not in smaller classes.
  • Kane, T.J.,  & Staiger, D.O. (2005). Using imperfect information to identify effective teachers. Unpublished Paper. School of Public Affairs, University of California–Los Angeles. Cited in Gordon, R., Kane, T.J.,  & Staiger, D.O. (2006). Identifying Effective Teachers Using Performance on the Job. Hamilton Project. This study found that “when the Los Angeles Unified School District needed to triple its hiring of elementary teachers following the state’s class-size reduction initiative in 1997, the district was able to do so without experiencing a reduction in mean teacher effectiveness, even though a disproportionate share of the new recruits were not certified. “
  • Fidler, P., Phd. (2002). The Impact of class size reduction on student achievement.  Los Angeles Unified School District, Publication No. 109. “The purpose of this study was to examine the impact of class size reduction (CSR) on achievement among 3rd, 4th, and 5th grade students with different numbers of years of participation in CSR…. We believe that CSR will help to increase student achievement, especially for students who need it the most: low SES students, limited English-speaking students, and those students in inner-city schools…. It can be concluded from the results of this study that CSR does help to increase language achievement gains, especially for ELL students.”
  • Jepsen, C. & Rivkin, S. (2002). Class Size Reduction, Teacher Quality, and Academic Achievement in California Public Elementary Schools. Public Policy Institute of California.  This study showed that in the five largest school districts in California other than Los Angeles, that is, San Diego, San Francisco, Long Beach , Oakland and Fresno, class size reduction raised the proportion of third graders who exceeded the national median score by 10.5% in math, and 8.4% in reading, after controlling for all other factors. It also showed that the more black students in school, the greater the gains –14.7% more students exceeding the national median in math, 18.4% more in reading in schools with 100% black student enrollment (again in urban districts aside from L.A.).
  • Urman, H. (2000). The Effects of class size reduction on students’ achievement,  English proficiency designation, retention in grade, and attendance. Vital Research. This study found that smaller classes increased reading scores in the SAT-9 exams by 9.5%, math scores by 13.9% and language scores by 14.5%, with approximately double these gains for “high need” students. No major changes in either the double gains for “high need” students. No major changes in either the curriculum or instruction had taken place over this time period that might have led to these improvements.
  • Stasz, C. and Stecher, B.M. (2000). Teaching Mathematics and Language Arts in reduced size and non-reduced size classrooms.  Educational Evaluation and Policy Analysis, 22, 313-329. Two controlled studies show significant gains in Los Angeles, with effect sizes that increased the longer the child remained in smaller classes. Some of these gains were shown to persist into fourth and fifth grades.Fidler, P., Phd. (2002). The Relationship between teacher instructional techniques and characteristics and student achievement in reduced size classes. Los Angeles Unified School District, Publication No. 120.“The purpose of this study was to examine the impact of class size reduction (CSR) on achievement among 3rd, 4th, and 5th grade students with different numbers of years of participation in CSR…. We believe that CSR will help to increase student achievement, especially for students who need it the most: low SES students, limited English-speaking students, and those students in inner-city schools…. It can be concluded from the results of this study that CSR does help to increase language.”
  • Stecher, B.M. & Bohrnstedt, G.W. (Eds.). (2002). Class size reduction in California: Findings from 1999–00 and 2000–01. Sacramento, CA: California Department of Education. The authors found California students who were in smaller classes only in third grade also performed better, significantly compared to those who remained in a large class in 1997-98 and 1998-99. The differences in scores were equivalent to effect sizes of about 0.04 to 0.1 standard deviation, about the same size as students placed in small classes for only one year in the Tennessee STAR studies. 
  • Fidler, P., Phd. (2002). The Impact of class size reduction on student achievement.  Los Angeles Unified School District, Publication No. 109. “The purpose of this study was to examine the impact of class size reduction (CSR) on achievement among 3rd, 4th, and 5th grade students with different numbers of years of participation in CSR…. We believe that CSR will help to increase student achievement, especially for students who need it the most: low SES students, limited English-speaking students, and those students in inner-city schools…. It can be concluded from the results of this study that CSR does help to increase language achievement gains, especially for ELL students.”
  • Gallagher, L.P. (2002). Class Size Reduction and Teacher Migration, 1995–2000. CSR Research Consortium Capstone Report (2002), see pp. C16-C17, esp. figure C-11. Shows that class size reduction in California led to higher rates of teacher retention, especially among novice teachers, which would be expected to result in a more effective, experienced teaching force over all. Within a few years, the rate of teachers who left high-poverty schools to work in more affluent areas was much lower than before class sizes were reduced.

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Class size data

  • New York City Department of Education. (2010). 2009-10 Updated Class Size Report (updated on 2/16/10). Excel versions of the 2009-10 Updated Class Size Report which includes class size data at the citywide, borough, district, and school levels.
  • ECS StateNote. (2009). State policies focusing on class-size reduction. State Notes: Class Size. Updated by Kenneth Zinth, Education Commission of the State, Dever, CO. This document updates a 2005 ECS StateNote, providing a detailed look at class-size reduction initiatives in 23 states, including information about funding and legislative provisions.
  • New York City Department of Education. (2009).2008-09 Updated Class Size Report (updated on 2/17/09). Excel versions of the 2008-09 Updated Class Size Report which includes class size data at the citywide, borough, district, and school levels.
  • New York State Education Department. (2008). 2007-08 Average Class Size. IRS: Information and Reporting Services, PMF Standard Statistical Runs. State-wide class size data, aggregated by district, county and region. Retrieved from http://www.p12.nysed.gov/irs/pmf/2007-08/home.html.
  • New York City Department of Education. (2008).2007-08 Updated Class Size Report (updated on 2/15/08). Excel versions of the 2007-08 Updated Class Size Report which includes class size data at the citywide, borough, district, and school levels.
  • New York State Education Department. (2007). 2006-07 Average Class Size. IRS: Information and Reporting Services, PMF Standard Statistical Runs. State-wide class size data, aggregated by district, county and region. Retrieved from http://www.p12.nysed.gov/irs/pmf/2006-07/home.shtml.
  • New York City Department of Education. (2007).2006-07 Class Size Report. Excel versions of the 2006-07 Class Size Report which includes class size data at the citywide, borough, district, and school levels.
  • New York State Education Department. (2006). 2005-06 Average Class Size. IRS: Information and Reporting Services, PMF Standard Statistical Runs. State-wide class size data, aggregated by district, county and region. Retrieved from http://www.p12.nysed.gov/irs/pmf/2005-06/home.shtml.
  • New York State Education Department. (2005). 2004-05 Average Class Size. IRS: Information and Reporting Services, PMF Standard Statistical Runs. State-wide class size data, aggregated by district, county and region. Retrieved from http://www.p12.nysed.gov/irs/pmf/2004-05/home.htm
  • New York State Education Department. (2004). 2003-04 Average Class Size. IRS: Information and Reporting Services, PMF Standard Statistical Runs. State-wide class size data, aggregated by district, county and region. Retrieved from http://www.p12.nysed.gov/irs/pmf/2003-2004/home.htm.
  • New York State Education Department. (2003). 2002-03 Average Class Size. IRS: Information and Reporting Services, PMF Standard Statistical Runs. State-wide class size data, aggregated by district, county and region. Retrieved from http://www.p12.nysed.gov/irs/pmf/2002-2003/home.html.
  • New York City Department of Education. (2003). Executive summary — Cohort 2001: An exit survey of new teachers who left the New York City public schools within one year. Prepared by Fred Smith. Exit survey of NYC public school teachers who left after only one year of teaching, the majority of whom (60%) left to other jobs elsewhere in field of education. While monetary matters contributed to their decision to leave, a desire for better working conditions was a greater consideration.  Among the most important factors causing teachers to leave their jobs at NYC public schools were Disciplinary issues (46%) Student Behavior (38%), Classroom Management Issues, and Class Size (34% each).  Other important factors were Student Behavior (38%). Student Disrespect for Teachers (37%), Inability of Students to Stay Focused on Learning Tasks (23%) and Student Conflicts (22%).  Since research shows that smaller classes have a positive impact on all these factors, this suggests the central role class size played in causing high teacher attrition rates in NYC public schools.
  • New York State Education Department. (2002). 2001-02 Average Class Size. IRS: Information and Reporting Services, PMF Standard Statistical Runs. State-wide class size data, aggregated by district, county and region. Retrieved from http://www.p12.nysed.gov/irs/pmf/2001-2002/home.html.
  • New York State Education Department. (2001). 2000-01 Average Class Size. IRS: Information and Reporting Services, PMF Standard Statistical Runs. State-wide class size data, aggregated by district, county and region. Retrieved from http://www.p12.nysed.gov/irs/pmf/2000-2001/home.html.

 

 

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