Publication Date

February 2001


[Excerpt] When we ask whether class size matters for achievement, it is essential to ask also, how class size matters. This is important for three reasons. First, if we can observe not only achievement differences, but also the mechanisms through which the differences are produced, this will increase our confidence that the differences are real, and not an artifact of some unmeasured or inadequately controlled condition. Second, the effects of class size may vary in different circumstances, and identifying how class size affects achievement will help us to understand why the effects of class size are variable. Third, the potential benefits of class size reduction may be greater than what we observe. For example, suppose class size reductions aid achievement, but only when teachers modify instructional practices to take advantage of the smaller classes. If a few teachers make such modifications, but most do not, then understanding how class size affects achievement in some cases will help reveal its potential effects, even if the potential is generally unrealized.


Suggested Citation
Ehrenberg, R. G., Brewer, D. J., Gamoran, A. & Willms, J. D. (2001). The class size controversy (CHERI Working Paper #14). Retrieved [insert date], from Cornell University, ILR School site:

Required Publisher Statement
Published by the Cornell Higher Education Research Institute, Cornell University.