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...

We study whether a higher share of immigrant pupils affects the school performance of natives using aggregate multi-country data from PISA. We find evidence of a negative and statistically significant relationship. The size of the estimated effect is small: doubling the share of immigrant pupils...