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.

Improving academic outcomes for economically disadvantaged students has proven challenging, particularly for children at older ages. We present two large-scale randomized controlled trials of a high-dosage tutoring program delivered to secondary school students in Chicago. One innovation is to use paraprofessional tutors to hold down cost, thereby increasing scalability. Participating in math tutoring increases math test scores by 0.18 to 0.40 standard deviations, and increases math and nonmath course grades. These effects persist into future years. The data are consistent with increased personalization of instruction as a mechanism. The benefit-cost ratio is comparable to many successful early childhood programs.