In Low-and Middle-Income Countries, there is a debate as to whether priority should be given to building preschools or improving the existing primary education system. To answer this question, we partnered with the Government of Côte d'Ivoire to implement a randomized controlled trial aiming to measure the relative impact of opening public preschools and of a multi-faceted intervention designed to improve the quality of primary school education. Both had positive effects on children' skills, but the preschools proved more cost-effective over the duration of the pilot. However, evidence suggests that this conclusion may not always hold, especially in the longer term. Finally, the two interventions appear to be substitutes, as their simultaneous implementation did not improve children's outcomes beyond what was achieved by each intervention when implemented separately.