How Much Does Class Size Matter?

There’s little debate among teachers that class size matters. One survey found that nine in ten teachers said that smaller classes would strongly boost student learning. “Huge class sizes are a challenge because it makes it hard to focus on individual students who are struggling or who are ready to go on to the next level,” one high school teacher explained. But some education policymakers and pundits remain skeptical, arguing that reducing class sizes is of limited value and diverts money from more effective investments. So how much does class size matter? And is it really the best use of finite educational dollars?

Students often do better in smaller classes, but there’s no agreement on exactly how much better, and it remains an open question whether or not class size reduction is a particularly good use of funds that could go elsewhere. All told, “the impact of smaller classes would depend on many factors,” said Northwestern University economist Diane Schanzenbach, “including whether funds are reduced for other student supports, the quality of the newly hired teachers needed to staff the smaller classes, and adequate availability of classroom space.”

The most famous and rigorous study of class size reduction took place in Tennessee beginning in 1985, when some kindergarten students were randomly assigned to unusually small classes through third grade. Test scores in the classes of 13 to 17 students quickly surpassed scores in the larger classes of 22 to 25. Those gains persisted for years. Other studies in California, Minnesota, New York City, North Carolina, Texas, and Wisconsin have shown lower class sizes boost test scores, too.

A few studies have also found other benefits, with smaller classes leading to greater classroom engagement and higher attendance. In Tennessee, researchers later found that students in smaller classes in early grades were also more likely to attend and graduate from college.

These studies do not agree on how much improvement schools can expect from smaller class sizes, however. In some research, the impact of small classes is more modest than the large gains seen in Tennessee. In Minnesota, for instance, 10 fewer kids in class translated into a tiny increase in test scores.

There are also a few instances where smaller classes didn’t seem to improve test scores at all, including in studies in Connecticut and Florida. “Most studies find at least some evidence of positive effects of smaller classes, but the size of these benefits is inconsistent,” wrote Urban Institute researcher Matt Chingos.

Some argue that putting resources into reducing class sizes — which requires more teachers and often additional classroom space — is misguided. Schools should focus on getting and keeping better teachers, not simply adding teachers, with the resources they have, they argue. That comparison implies that there is a straightforward and less costly way to improve teacher quality, but it’s not clear that’s the case.

Allison Green
Boston Tutoring Services