Redshirting gives younger athletes an additional year to develop skills and extends their playing eligibility, since colleges allow these freshmen five years to attend and compete. On the other end of the student age spectrum, many parents of preschoolers have bought into this concept, choosing to delay their child's entry into kindergarten for a…

We estimate the effects of relative age in kindergarten using data from an experiment where children of the same age were randomly assigned to different kindergarten classmates. We exploit the resulting experimental variation in relative age in conjunction with variation in expected kindergarten entry age based on birth date to account for…

Older children outperform younger children in a school-entry cohort well into their school careers. The existing literature has provided little insight into the causes of this phenomenon, leaving open the possibility that school-entry age is zero-sum game, where relatively young students lose what relatively old students gain. In this paper, we…