New evidence on the effect of time in school on early achievement. Econ WPA. Retrieved 15

This study exploits two features of the Dutch schooling system to esti-mate the effect of expanding enrollment possibilities on test scores of young children. One feature is that children are allowed to enroll in school on their fourth birthday. The other that children having their birthday before, dur-ing 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. Allowing disadvantaged pupils to start school one month earlier increases their test scores on aver-age 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