We exploit rules of class formation to identify the causal effect of increasing the number of immigrants in a classroom on natives test scores, keeping class size constant (Pure Composition Effect). We explain why this is a relevant policy parameter although it has been neglected so far. We show...

An important component of the long-run cost of a war is the loss of human capital, suffered by children of schooling age who receive less education because of the war. This paper shows that in the European countries involved in World War II, children who were ten years old during the conflict...