Many argue that childcare costs limit the labor supply of mothers, though existing evidence has been mixed. Using a child's eligibility for public kindergarten in a regression discontinuity instrumental variables framework, I estimate how use of a particular subsidy, public school, affects maternal labor supply. I find public school enrollment increases only the employment of single mothers without additional young children. I compare this result to previous work, focusing on striking increases in a similar setting but earlier period (Gelabch 2002). Differences in the population of mothers, labor supply, and patterns of lifecycle events likely drive the discrepancy in results. (Contains 10 tables and 16 footnotes.)