A Primer on Class-Size Reductions, from Brookings

By Sean Cavanagh — May 16, 2011 2 min read
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States and school districts around the country are coping with what are probably the worst budget conditions they’ve faced in decades, a predicament that is pushing them toward what has always been a politically unpopular policy option: raising class sizes.

Research has generally shown that keeping class sizes low has a positive effect on students’ academic achievement at early grades, and among disadvantaged students. The effects at higher grades tend to be less impressive. As state legislatures and school boards play the class-size game, a new paper from the Brookings Institution tries to lay out what research says about class-size reductions—and perhaps just as important, what research hasn’t told us yet.

One of the challenges for elected officials and educators is that there is no research in the United States that directly compares class-size reductions to alternative investments, note the authors, Grover J. Whitehurst and Matthew M. Chingos. That means, for example, that comparing the benefits of $20 billion worth of spending on keeping class sizes small, versus $20 billion in spending on paying teachers more, involves a lot more guesswork than science.

But given current budget pressures, the authors say, if states want to keep class sizes low, they should consider doing it where research shows it’s most likely to make an impact—with disadvantaged students in early grades.

As is often the case in policymaking, elected officials today are making huge decisions about class size with imperfect information. How huge? By the authors’ rough calculation, a one-student increase in the pupil-to-teacher ratio would save U.S. schools $12 billion per year—and would decrease the teaching workforce by 7 percent.

The success of changes of that magnitude are likely to depend on how they’re implemented. It stands to reason, the authors say, if large numbers of teachers are laid off without regard to their effectiveness (such as through so-called “last-in-first-out” policies), then it could have a negative impact on student achievement.

Whitehurst, the former director of the federal Institute of Education Sciences, and co-author Chingos, also caution against cherry-picking class-size data, and taking research out of context. For instance, the authors note that according to a number of well-designed studies, student achievement actually increased when class sizes rose in the United States prior to World War II. But the relevance of that research is limited, they say, because way that schools are organized, the nature of the teaching profession, and other factors have changed so much since then.

Keep a close eye on how states and school districts choose to raise class size—for specific grade levels, or for specific populations of students—as they finish crafting budgets for next year.

A version of this news article first appeared in the State EdWatch blog.