We evaluate the effect of child care versus maternal time inputs on child cognitive development using single mothers from the NLSY79. To deal with nonrandom selection of children into child care, we exploit the exogenous variation in welfare policy rules facing single mothers. In particular, the 1996 welfare reform and earlier state-level policy changes generated substantial increases in their work/child care use. We construct a comprehensive set of welfare policy variables and use them as instruments to estimate child cognitive ability production functions. In our baseline specification, we estimate that a year of child care reduces child test scores by 2.1%.

Globally, access to preschool has increased dramatically but its quality is often poor. We evaluate two interventions aimed at improving the quality of public preschools in Colombia. The first, designed by the government and rolled-out nationwide, provided preschools with significant extra funding, mainly earmarked for hiring teaching assistants (TAs). The second, for a small additional cost, also offered training for existing teachers. We show that the first intervention did not improve child development, while the second led to significant improvements in children’s cognitive development, especially for those from more disadvantaged backgrounds. We argue these dramatic differences can be explained by the two interventions having different impacts on teachers’ behavior. The first led teachers to reduce the time they spent in the classroom, including on learning activities. The addition of the training offset this adverse effect of TA provision on teachers’ learning activities and improved the quality of teaching.