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Heterogeneous Class Size Effects: New Evidence from a Panel of University Students


  •  We thank the editor, Marianne Bertrand, and three anonymous referees for comments that have helped improve the article. We have also benefited from discussions with Peter Arcidiacono, Decio Coviello, Michael Kremer, Lisa Lynch, Michele Pellizzari, Cecilia Rouse and numerous seminar audiences. We thank all those involved in providing the data. Selim Gulesci provided excellent research assistance. This article has been screened to ensure no confidential information is revealed. All errors are our own.


Using administrative records from a UK university, we present evidence on the effects of class size on students’ test scores. We estimate non-linear class size effects controlling for unobserved heterogen-eity of students and faculty. We find that: (i) at the average class size, the effect size is −0.108; (ii) the effect size is negative and significant only for the smallest and largest ranges of class sizes and zero in intermediate class sizes; (iii) students at the top of the test score distribution are more affected by changes in class size, especially when class sizes are very large.