Holding younger students back because of their age harms student achievement

This study analyzes the effect of age-based retention on school achievement at different stages of education. Using international data from multiple waves of the PISA international assessment test, the author finds that grade retention in primary school harms student achievement across the distribution, while delayed school entry can produce positive results for those at the lower end. The identified local average treatment effect indicates that letting students retain in primary school because of a low relative age is harmful for their future school achievement.