reliable electronic data. Kindergarten participation was also excluded since it is universal.Evidence of selection bias in ECCE choices compelled us to use Propensity Score Matching (PSM). Propensity Score Matching was used to estimate the effect of public ECCE on academic achievement by: (a) matching children who attended public ECCE (N = 31,947)with children who did not attend ECCE programs (N = 54,571)according to their probability of attending public ECCE (propensityscore) and; (b) comparing their SIMCE 2008 test scores.