Redshirting, Compulsory Schooling Laws, and Educational Attainment

A wide literature uses date of birth as an instrument to study the causal effects of educational attainment. This paper shows how parents delaying their children's initial enrollment in kindergarten, a practice known as redshirting, can make estimates obtained through this identification framework all but impossible to interpret. A latent index model is used to illustrate how the monotonicity assumption in this framework is violated if redshirting decisions are made in a setting of essential heterogeneity. Empirical evidence is presented from the ECLS-K data set that favors this scenario; redshirting is common and heterogeneity in the treatment effect of educational attainment is likely a factor in parents' redshirting decisions