Does class size really matter? A Chalkbeat look at the research

Recently Matt Barnum reviewed the research on class size for Chalkbeat. Excerpts of the piece appear below:

The key takeaways: 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.”

Smaller does seem better when it comes to class size. 

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.

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.

It’s not clear how big those benefits are, though

These studies do not agree on how much improvement schools can expect from smaller class sizes. In some research, the impact of small classes is more modest than the large gains seen in Tennessee. 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.

Smaller classes mean hiring lots of teachers, which is complicated

Substantially reducing class size generally requires schools to go on a hiring binge in order to staff the new classes — and those new teachers are often less experienced and effective than their peers. That means the benefits from lower class size may be partially counteracted by reductions in teacher quality, which has been shown in studies from California and New York City.

Lowering class sizes comes with tradeoffs

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.

There’s still more to learn about how class sizes affect kids, but the perspectives of teachers and parents should be taken seriously

In education policy circles, you’ll often hear confident claims about class size reduction. In addition, many parents and teachers say class size makes a difference. 

For more, see: