We estimate the impact of having attended centre-based daycare institutions during early childhood on math test scores at the fourth grade level of elementary school. We find evidence that daycare attendance has a net impact on math proficiency, and that the effects are heterogeneous. The effect of daycare and kindergarten attendance on proficiency varies according to mother's education. The effects of the impact of daycare vary from -0.28 standard deviation for mothers with no education to 0.42 standard deviation for mother's with college or more. (author abstract)