Long-term effects of class size

This paper evaluates the long-term effects of class size in primary school. We use rich data from Sweden and exploit variation in class size created by a maximum class size rule. Smaller classes in the last three years of primary school (age 10 to 13) are beneficial for cognitive and non-cognitive ability at age 13, and improve achievement at age 16. Most importantly, we find that smaller classes have positive effects on completed education, wages, and earnings at age 27 to 42. The estimated wage effect is much larger than any imputed estimate of the wage effect, and is large enough to pass a cost-benefit test.