A new policy brief validates what teachers have known all along: Class size matters. The brief, which summarizes academic literature on the topic, finds class size makes a difference when it comes to everything from test scores to broader life outcomes — especially for low-income and minority children.
The policy brief from the National Education Policy Center was authored by Diane Whitmore Schanzenbach of Northwestern University and recommends the following to policymakers.
- Money saved by increasing class sizes will result in social and educational costs in the future.
- Increases in class size are most harmful to minority and low-income students.
- Lower class size has a cost, but it may prove to be a cost-effective policy overall.
Schanzenbach points out that some previous reviews of research have concluded that class size does not affect student learning. However, she writes that many of these reviews relied on poor-quality research, including studies that failed to isolate the causal impact of class size.
When Schanzenbach examined well-designed studies, her findings were quite different. One randomized study — the gold standard of social science research — showed that “students’ achievement on math and reading standardized tests improved by about 0.15 to 0.20 standard deviations (or 5 percentile rank points) from being assigned to a small class of 13-17 students instead of a regular sized class of 22-25 students.”