Are Larger Class Sizes a Problem Worth Worrying About?

In recent years, budget cuts have caused increases in class size in states across the nation.  Between 2009 and 2010, the pupil-teacher ratio in the U.S. increased by more than half a student for the first time since the Great Depression.  The nationwide increase is quite small, but some states have experienced larger changes than others.  A notable outlier is California, where the pupil-teacher ratio (a proxy for class size) increased by more than 4 students between 2009 and 2010, an increase of more than 20 percent.

Times of fiscal austerity renew debates about the best way to spend limited educational resources.  Class size is at the center of these debates because the size of the classes in which students are educated is one of the most important drivers of educational costs.  Smaller classes mean that more teachers must be hired and more classrooms built.  Conversely, allowing class sizes to increase can be a way to absorb budget cuts without cutting other programs such as athletics and the arts.

In “Class Size and Student Outcomes: Research and Policy Implications," Matthew M. Chingos reviews the mixed research on the effects of class size.  Most studies find at least some evidence that smaller classes have positive effects, but the size of these benefits is inconsistent across studies and often small.  The substantial costs of reducing class size coupled with these modest benefits implies that many school systems in the U.S. have overinvested in class-size reduction and that increasing class size in some situations may represent a budget-cutting strategy that minimizes harm to students.

Research on class size is particularly relevant in California, which spent more than $1 billion per year in the late 1990s to reduce class size in the early grades from 30 to 20 students.  This policy has unraveled in recent years as schools face severe budget cuts.  Research on the California policy is limited by data constraints, but suggests that the policy’s effects were small and dampened by how quickly it was implemented.  The effects of rising class sizes in California are also likely to depend on how the changes are implemented.  If the teachers to be laid off are chosen in a way largely unrelated to their effectiveness, such as “last in first out,” then the resulting increase in class size could well have a negative effect on student achievement.  But if schools choose the least effective teachers to let go, then the effect of increased teacher quality could make up for some or all of any negative effect of increasing class size.

The full study is in Chingos, M. M. (2012), Class Size and Student Outcomes: Research and Policy Implications. Journal of Policy Analysis and Management 32 (2), 411–438.