Preliminary

School starting age/date rules mean that there is a continuum of ages within each starting class – with the “oldest ” children being approximately twenty percent older than the “youngest ” children at school entry. We provide substantial evidence that these initial maturity differences have long lasting effects on student performance across OECD countries. In particular, the oldest students score 3-14 percentiles higher than the youngest students in grade four, and 3-9 percentiles higher in grade eight, depending upon the country. In fact, data from Zealand shows that the oldest children are even more likely to complete college. Taken together, these findings point to important early relative maturity effects that propagate themselves into adulthood through the structure of education systems