A Meta-Analysis of Class Sizes and Ratios in Early Childhood Education Programs - Are Thresholds of Quality Associated With Greater Impacts on Cognitive, Achievement, and Socioemotional Outcomes

Oct 15, 2026

Meta-analytic evidence evaluates how class size and child–teacher ratio relate to program effect sizes for cognitive, achievement, and socioemotional outcomes in U.S. early childhood education programs evaluated from 1960–2007. Both structural measures show nonlinear patterns: for child–teacher ratios at or below 7.5:1, reducing by one child per teacher predicts a 0.22 SD higher effect; for class sizes 15 or fewer, one fewer child predicts 0.10 SD higher. No clear association emerges for larger classes/ratios, while socioemotional results are less definitive due to limited data.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages22

Reading Time55 min

AccessFree to download

Background

Structural quality indicators in ECE

Evidence and theoretical models

Interactions among children, peers, and teachers

Expected benefits of smaller classes and lower ratios

Evidence base and limitations

Educational Evaluation and Policy Analysis September 2017, Vol. 39, No. 3, pp. 407–428 DOI: 10.3102/0162373716689489 © 2017 AERA. [http://eepa.aera.net](http://eepa.aera.net) A Meta-Analysis of Class Sizes and Ratios in Early Childhood Education Programs: Are Thresholds of Quality Associated With Greater Impacts on Cognitive, Achievement, and Socioemotional Outcomes? Jocelyn Bonnes Bowne Harvard Graduate School of Education Katherine A. Magnuson University of Wisconsin-Madison Holly S. Schindler University of Washington Greg J. Duncan University of California, Irvine Hirokazu Yoshikawa New York University This study uses data from a comprehensive database of U.S. early childhood education program evaluations published between 1960 and 2007 to evaluate the relationship between class size, child– teacher ratio, and program effect sizes for cognitive, achievement, and socioemotional outcomes. Both class size and child–teacher ratio showed nonlinear relationships with cognitive and achievement effect sizes. For child–teacher ratios 7.5:1 and lower, the reduction of this ratio by one child per teacher predicted an effect size of 0.22 standard deviations greater. For class sizes 15 and smaller, one child fewer predicted an effect size of 0.10 standard deviations larger. No discernible relationship was found for larger class sizes and child–teacher ratios. Results were less clear for socioemotional outcomes due to a small sample. Keywords: child-teacher ratio; class size; early childhood education; meta-analysis Decades of program evaluation research have shown that center-based early childhood education (ECE) programs can improve children’s cognitive and social development (Camilli, Vargas, Ryan, & Barnett, 2010). As a result, policymakers and educators have pushed for public funding to expand access to ECE. With increased funding, most children now attend ECE before entering elementary school (Burgess, Chien, Morrissey, & Swenson, 2014; Magnuson & Shager, 2010). Yet, with increased enrollment has come greater scrutiny about whether ECE programs are delivering on the promise of improved school readiness that fueled their growth. Increasingly, researchers and policymakers are paying greater attention to how to improve children’s early learning by increasing the effectiveness and educational benefits of existing ECE programs. Although experts agree that the most effective center-based ECE programs provide developmentally appropriate and enriching social and academic environments, most concede that it is hard to define and measure these aspects of settings in cost-effective ways. Therefore, policymakers have often focused on structural dimensions of program quality—aspects of ECE program design that can Bowne et al. be easily defined, measured, and legislated—such as class sizes, teacher education, and child–teacher ratios. These aspects of program design are thought to affect children indirectly, by promoting or impeding safe and positive care environments. As a result, requirements for minimum standards related to structural indicators have long been part of child care business licensing requirements and are now increasingly central features of state and local quality rating and improvement systems (QRIS), as well as Head Start performance standards (U.S. Department of Health and Human Services, 1996). Despite the appeal of using structural indicators to assess program quality, empirical evidence on the association between structural indicators and children’s learning is lacking. In this study, we use meta-analytic methods to estimate the association between two of the mostwidely used dimensions of ECE structural quality (class size and child–teacher ratio) and children’s cognitive and achievement outcomes in early childhood classrooms. Background Although ECE pedagogy may differ across programs, many theoretical models of early learning place interactions between children and their teachers,

FAQs

What data range and source does the study use for its meta-analysis?

It uses a comprehensive database of U.S. early childhood education program evaluations published between 1960 and 2007.

How do class size and child–teacher ratio relate to cognitive and achievement outcomes?

Both show nonlinear relationships with effect sizes for cognitive and achievement outcomes.

What do the results indicate for socioemotional outcomes?

Findings are less clear because the sample size for socioemotional outcomes is small.

Oct 15, 2026

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