Report: Small Changes in Class Size Have Little Impact

A new report from the Brookings Institution casts doubt on the effectiveness of efforts to reduce class size around the country. Analysts sifted through research on class-size reduction and reached a definitive conclusion: To have a meaningful effect on student outcomes, class size must drop by seven to 10 students, must occur in lower grades, and must target a specific population of students. National moves to cut class size — though costly — have typically done none of these, instead making small, across-the-board reductions.

In fact, the study finds that an increase or decrease of a few students seems to have little to no impact on student performance. To illustrate how little these small changes in class size matter, analysts drew on research findings to project how adding or subtracting one student might affect results on the Texas Assessment of Knowledge and Skills.

Given the test’s statewide mean of 700, decreasing class size by one student would raise the mean score to 701.5. Increasing the class by one student would drop the mean score to 698.5. For some perspective, the scale scores of white and black students differ by a staggering 65 points. What’s more, the quality of a teacher has been shown to have a much greater impact on student achievement than class size. 

In sum, changing class size by one or two students in a classroom has a negligible effect on learning. To really improve our schools, policymakers should rethink the massive investment in reducing class size — and turn their attention instead to growing the effectiveness of our teaching force.