Class size reduction efforts reduce the ratio of students to educators in a classroom. Class size refers to the number of students assigned to a classroom; measures of class size do not account for the number of educators in the classroom, often called the student-teacher ratio. In K-3 elementary schools, the average difference between student-teacher ratio and classroom size in the 2013-14 school year was 9 or 10 students; an elementary school with a 16:1 school-wide student-teacher ratio had an average class size of 25 or 26 students1.
Expected Beneficial Outcomes (Rated)
Increased academic achievement
Other Potential Beneficial Outcomes
Increased high school completion
Evidence of Effectiveness
There is some evidence that smaller classes modestly improve academic outcomes2, 3, 4, 5, especially when implemented in kindergarten or first grade6, 7, 8. However, class size reduction efforts typically have small effect sizes, perhaps due to continued use of teaching methods applied in larger classes9. Additional evidence is needed to confirm effects.
A small first grade class can modestly improve outcomes for students who were in larger kindergarten classes6. Overall, reductions in class size appear to benefit students who struggle in school more than high-achieving students, and smaller classes appear to have smaller achievement gaps than classes with more children10. Studies of Tennessee’s Student–Teacher Achievement Ratio (TN STAR) experiment indicate that small classes have the greatest benefits for children from households with low incomes and minority students11, and improvements in reading skills among minority students persist for at least five years3. Small classes from kindergarten to second grade may improve high school completion rates for children from low income backgrounds, especially those who are placed in a small third grade class4.
Smaller classes appear to have modest positive effects on academic outcomes when teachers adopt teaching practices that take advantage of smaller class environments8, increasing individual attention and student-teacher interactions12. Class size reduction efforts also appear more likely to affect academic outcomes when implemented with professional development efforts that support teacher and staff use of teaching techniques, classroom management, and student interaction strategies suited to small class environments13. Class size reductions may also improve student and teacher work environments9.
Class size reduction efforts frequently require additional classroom space, though principals willing to fundamentally restructure school space can overcome space challenges. Principals can also deploy funding streams creatively to reduce class size14. Researchers suggest that many interventions can more cost effectively improve academic achievement than class size reduction efforts; tutoring and professional development are two examples7, 9.
Impact on Disparities
In 2009, 23 states had enacted policies to reduce class size to a level below 20 students per classroom; 15 of those states focus on students in grades K-315. By 2010, 35 states had laws restricting the number of students allowed in a general education classroom. Following the economic downturn, however, 19 states relaxed or eliminated these laws16.
In 2016, Arizona introduced a bill for a class size reduction and teacher retention program in grades K-317.
WI DPI-SAGE - Wisconsin Department of Public Instruction (WI DPI). Student achievement guarantee in education (SAGE) program.
Burch 2010* - Burch P, Theoharis G, Rauscher E. Class size reduction in practice: Investigating the influence of the elementary school principal. Educational Policy. 2010;24(2):330-58.
* Journal subscription may be required for access.
1 NEA-State rankings 2014 - National Education Association (NEA). Rankings of the states 2013 and estimates of school statistics 2014: For population, school enrollment, classroom teachers, student expenditures, general financial resources, and school revenue.
2 Konstantopoulos 2011* - Konstantopoulos S. How consistent are class size effects? Evaluation Review. 2011;35(1):71-92.
3 Nye 2004* - Nye B, Hedges LV, Konstantopoulos S. Do minorities experience larger lasting benefits from small classes? Journal of Educational Research. 2004;98(2):94-100.
4 Finn 2005* - Finn JD, Gerber SB, Boyd-Zaharias J. Small classes in the early grades, academic achievement, and graduating from high school. Journal of Educational Psychology. 2005;97(2):214-23.
5 Cho 2012* - Cho H, Glewwe P, Whitler M. Do reductions in class sizes raise students' test scores? Evidence from population variation in Minnesota's elementary schools. Economics of Education Review. 2012;31(3):77-95.
6 Ding 2010* - Ding W, Lehrer SF. Estimating treatment effects from contaminated multiperiod education experiments: The dynamic impacts of class size reductions. Review of Economics and Statistics. 2010;92(1):31-42.
7 Brookings-Chingos 2011 - Chingos MM, Whitehurst GJ. Class size: What research says and what it means for state policy. Washington, DC: Brookings Institution; 2011.
8 Watson 2013 - Watson K, Handal B, Maher M, McGinty E. Globalising the class size debate: Myths and realities. Journal of International and Comparative Education. 2013;2(2):72-85.
9 Hattie 2005* - Hattie J. The paradox of reducing class size and improving learning outcomes. International Journal of Educational Research. 2005;43:387-425.
10 Bosworth 2014* - Bosworth R. Class size, class composition, and the distribution of student achievement. Education Economics. 2014;22(2):141-165.
11 Reynolds 2010a* - Reynolds AJ, Magnuson KA, Ou SR. Preschool-to-third grade programs and practices: A review of research. Children and Youth Services Review. 2010;32(8):1121-31.
12 Blatchford 2011* - Blatchford P, Bassett P, Brown P. 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. 2011;21(6):715-730.
13 Harker 2004 - Harker R. Class size and student attainments: Research and strategic implementation. Massey University. 2004.
14 Burch 2010* - Burch P, Theoharis G, Rauscher E. Class size reduction in practice: Investigating the influence of the elementary school principal. Educational Policy. 2010;24(2):330-58.
15 ECS-Zinth 2009 - Zinth K. State policies focusing on class-size reduction. Denver: Education Commission of the States (ECS); 2009.
16 Ed Week-Class size 2011 - Education Week. Issues A-Z: Class size. Editorial Projects in Education Research Center. 2011.
17 NCSL-Early ed tracking 2016 - National Conference of State Legislatures (NCSL). 2016 Early education legislative tracking. 2016.
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