Research studies showing the benefits of class size reduction

Institute of Education Sciences, US Department of Education, “Identifying and Implementing Educational Practices Supported by Rigorous Evidence: A User Friendly Guide,” Dec. 2003. Class size reduction identified as one of four K-12 education reforms proven to increase learning.

Raj Chetty et. al. “How Does your Kindergarten classroom affect your earnings?  Evidence from Project Star,” NBER Working Paper 16381, http://www.nber.org/papers/w16381; 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.

D. McLaughlin and Gili Drori, School-Level Correlates of Academic Achievement, U.S. Dept. of Education, 2000. 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.

Spyros Konstantopoulos and Vicki Chun, “What Are the Long-Term Effects of Small Classes on the Achievement Gap? Evidence from the Lasting Benefits Study,” American Journal of Education 116, November 2009.  A summary of the effects of smaller classes on the achievement gap through eighth grade.  Effects significant in all tested subjects, and for those in smaller classes for four years, very substantial. “The results f… 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.”

Peter Blatchford  et.al. “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 2008: Paper showing that there is no threshold effect in terms of class size reduction yielding benefits; show gains for middle school students from smaller classes, which “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.”

Thomas Dee, “Teachers, Race, and Student Achievement in a Randomized Experiment,” Review of Economics and Statistics, February 2004. 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.

Peter Muennig and Steven H. Woolf, “Health and Economic Benefits of Reducing the Number of Students per Classroom in US Primary Schools,” American Journal of Public Health, published online September 27, 2007. 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 Oct. 16, 2007 summary in Slate magazine by Dr. Sydney Spiesel.

Philip Babcock and Julian R. Betts, “Reduced-class Distinctions: Effort, Ability and the Education Production Function,” NBER Working paper 14777, March 2009. Results indicate that small classes elicit enhanced effort and engagement by disadvantaged students.

Sarah Theule Lubienski et.al., “Achievement Differences and School Type: The Role of School Climate, Teacher Certification, and Instruction,” American Journal of Education 115, November 2008.  Multilevel analysis of National Assessment of Educational Progress (NAEP) mathematics data for over 270,000 fourth and eighth graders in over 10,000 schools finds that smaller class size is significantly correlated with higher achievement.

Thomas Dee and Martin West, “The Non-Cognitive Returns to Class Size, ” NBER Working Paper 13994, 2008. “Our results indicate that smaller classes in 8th grade lead to improvements in measures of student engagement ….Using the estimated earnings impact of these non-cognitive skills and the direct cost of a class-size reduction, the implied internal rate of return from an 8th-grade class-size reduction is 4.6 percent overall, but 7.9 percent in urban schools.”

Alan B. Krueger, Economic Considerations and Class Size, The Economic Journal, 113 (February 2003).  One of the most important contributions to the literature on class size, and an authoritative critique of Hanushek’s work.

Paul Barton, Parsing the Achievement Gap, Educational Testing Service, October 2003.  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.

Elizabeth Graue, et.al. “The Wisdom of Class-Size Reduction,” American Educational Research Journal, September 2007, Vol. 44, No. 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.”

Douglas D. Ready and Valerie E. Lee, “Optimal Context Size in Elementary Schools: Disentangling the Effects of Class Size and School Size,” Brookings Papers on Education Policy, 2006/2007, pp. 99-135. Study finds that class size rather than school size makes a positive difference, 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.”

Fatih Unlu, “California Class Size Reduction Reform: New Findings from the NAEP,” Princeton Univ., Nov. 2005; Study showing large gains from smaller classes in California.

Jeremy D. Finn et.al., “Small Classes in the Early Grades, Academic Achievement, and Graduating From High School,” Journal of Educational Psychology, 2005. 

SERVE, “How Class Size Makes a Difference,” 2002. 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.

Jeremy D. Finn, “Small Classes in American Schools: Research, Practice, and Politics,” Phi Beta Kappan, March 2002. A summary of the research by one of the premier STAR investigators.

STAR studies in Tennessee Formidable results from the historic large scale experiment in the history of education reform.

SAGE studies in Wisconsin; results from class size reduction in Wisconsin public schools from 1997 to 2004.

Bruce Biddle and David Berliner, “What Research Says About Small Classes and Their Effects.” Wested, 2002.

Alan B. Krueger and Diane M. Whitmore, “Would Smaller Classes Help Close the Black-White Achievement Gap?” from :Bridging the Achievement Gap, Brookings Institution Press 2002.

Debra Viadero, “Study Links Smaller Classes To Higher Earnings,” Education Week, October 25, 2000; Summary of Krueger’s economic analysis

Gerald Bracey, “Distortion and Disinformation about Class Size Reduction.”http://www.america-tomorrow.com/bracey/EDDRA/EDDRA4.htm

AEU Fact Sheet Number 1, “Class Sizes Do Matter.”

Education World, “Are smaller Classes the Answer?” 1998.

New South Wales,  Evaluations of class size reduction program, 2004-2008. “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, behaviour and social skills.”

Ivor Pritchard, “Reducing Class Size: What Do We Know?” US Department of Education, 1999.

Charles M. Achilles, “Small Classes, Big Possibilities,” The School Administrator, 1997.

Helen Pate-Bain; Effects of Class-Size Reduction in the Early Grades (K-3) on High School Performance,”April 1999.

David Grissmer, et.al. Improving Student Achievement: What State NAEP Test Scores Tell Us. RAND, 2000. State with higher per-pupil spending, lower class sizes and more preK have higher achievement levels.  Disadvantaged children are the most likely to gain benefits from such programs.

Leonie Haimson, Smaller is Better: First-hand Reports of Early Grade Class Size Reduction in NYC Public Schools, Educational Priorities Panel, 2000.

Valerie Wilson, Does Small Really Make a Difference?, University of Glasgow, June 2002. Good literature review on the effects of class size on teaching and student behavior.

Margaret Wang, “How Small Classes Help Teachers do Their Best, The National Center on Education in the Inner Cities, 2002.

Smaller classes in the upper elementary, middle and upper grades

C. H. Tienken and C. M. Achilles, “Making Class Size Work in the Middle Grades,” AASA Journal of Scholarship & Practice, Spring 2006/Vol. 3, No. 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.

Teachers of the Year talk about the need for smaller classes in the middle and upper grades:

D. McLaughlin and Gili Drori, School-Level Correlates of Academic Achievement, U.S. Dept. of Education, 2000. 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.  Student achievement was even more strongly linked to smaller classes in the upper rather than the lower grades.

Harold Wenglinsky, When Money Matters, Educational Testing Service, 1997. Shows how smaller classes in grades 4 and 8 are linked to higher test scores and improved student discipline.

National Council of Teachers of English, “More than a Number: Why Class Size Matters”.

Kenneth J. Bernstein, “Class size does matter,” Prince George’s and Montgomery Journal Newspapers, July 7, 2000. Excellent essay by a high school teacher, explaining why both smaller classes and a smaller teaching load is essential to improve student achievement.

Christian Dustmann et. al., “Class Size, Education and Wages“, Economic Journal February 2003. UK study showing high school students in small classes more likely to stay through graduation. See also Guardian UK summary.

Surveys

Public Agenda, “Sizing Things up“, 2001; 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.”

John M. Bridgeland, et.al., “The Silent Epidemic: Perspectives of High School Dropouts”, March 2006. National survey showing that 75% of high school dropouts say that if they had had been provided with smaller classes they would likely have stayed in school.

Public Agenda, “A Sense of Calling: Who Teaches and Why,”December,1999; 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.

Public Agenda, “Rolling Up Their Sleeves: Superintendents and Principals Talk About What’s Needed to Fix Public Schools,” 2003; 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%).

New York City Council Investigation Division,  Report on Teacher Attrition and Retention, 2004.http://www.nyc.gov/html/records/pdf/govpub/1024teachersal.pdf; 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”

Class size and race

Thomas Dee, “Teachers, Race, and Student Achievement in a Randomized Experiment,” Review of Economics and Statistics, February 2004. Study showing that student/teacher racial differences appear to negatively effect student achievement in regular size classes. Yet in small classes, students learn more, regardless of their teachers’ race.  

Michael Winerip, “Good Teachers + Small Classes = Quality Education,” New York Times, May 26, 2004.

Leonie Haimson, “The 50th anniversary of Brown vs. Board and the need to reduce class size,” May 17, 2004.

Class size data

OECD 2009; International comparisons of class size and other data. (xcl)