Persistent Classmates: How Familiarity with Peers Protects from Disruptive School Transitions

This paper investigates the effect of classmates' characteristics on students' achievement in high school, exploiting natural experiments occuring sporadically in French high schools. High school principals do not know their first-year students at the time they assign them to classes, so they do the allocation using only a limited set of information available on their registration files. In some rare cases, they have to assign to separate classes two or more students who look nearly identical, according to the information they observe in their files. We provide strong evidence suggesting that such first-year students are randomly assigned to their classes. When using these quasi-experiments to investigate the role of several classmates' characteristics, we find an important, positive effect of assignment with more persistent classmates, i.e. classmates who were already in the freshman's class before high school. We provide strong evidence that this result derives from the benefit of familiarity with peers, rather than from some unobserved ability characteristics of these classmates. The magnitude of the estimates suggests that grouping low-achieving freshmen who know each other could decrease their current repetition rate by around 13~percent, and raise their graduation rate by the same amount.