New evidence on the effect of time in school on early achievement

This study estimates the effect of expanding enrollment possibilities in early eduction on the achievement of young children. To do so it exploits two features of the Dutch schooling system. First, children are allowed to enroll in school on their fourth birthday. Second, children having their birthday before, during and after the summer holiday are placed in the same class. Together these features generate sufficient exogenous variation in children s potential time in school to identify its effects on test scores. We find that allowing disadvantaged pupils to start school one month earlier increases their test scores on average by 0.06 of a standard deviation. This effect is of the same magnitude for pupils with lower educated parents and for minority pupils. For non- disadvantaged pupils we find no effect. Results are similar for language and math scores.