Class size matters: Heterogeneous effects of larger classes on college student learning

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Colleges want to increase retention and graduation rates, but they are also under pressure to control costs. Increasing class size is a common method to reduce per student costs. This paper examines the relationship between class size and student achievement. Using data from a selective liberal arts college, we show that grades of students decrease as class size increases. Moreover, relatively vulnerable students such as first-years or those with low SAT scores experience on average larger negative effects from increases in class sizes. The findings suggest that attempts to control costs may harm students, particularly those least likely to graduate.