An Economic Analysis of the Optimal School Starting Age

This study develops and empirically applies an approach to identify the optimal school starting age. Postponing school entry involves a tradeoff between better learning through higher maturity and higher opportunity costs through foregone time. We model a Skill Technology Function, where learning becomes more effective as children mature, and use variation in month of birth for multiple countries from multiple data sources to empirically estimate the slope and the curvature of this function. To compare student performance at different exact ages, we express test scores in age equivalents. This allows us to separate starting age effects from age of testing effects, and shows that birth month effects stabilize relatively early. Our main conclusion is that higher starting ages improve achievement in both the short and the long run, but, for most conventional starting ages, this effect does not compensate for incurred opportunity costs.