Increasing class size is one of the key variables that policy makers can use to control spending on education. But the consensus among many education researchers is that smaller classes are effective in improving student achievement. This view has led to a policy of class size reductions in a number of US states, the UK, and the Netherlands. This…

Although experimental results indicate that smaller classes promote higher achievement in early elementary school, the broader literature on class-size effects is inconclusive. This seeming contradiction raises questions about the generalizability of experimental evidence, an issue that this article addresses by examining the effects of class size…