In low- and middle-income countries, 250 million children under the age of five are at risk of not reaching their full development potential, mainly due to low levels of cognitive stimulation and nutritional deficiencies. To limit the magnitude of this problem and associated cost to society, preschools are receiving increasing attention. However, while a growing number of studies demonstrate the positive impact of preschools in high-income countries, evidence remains scarce in lower-income countries. We will provide evidence on this issue by measuring the impact of the extensive preschool program launched in 2018 by King Mohammed VI, which aims to create 10,000 modern preschool units by 2023. Our project seeks to measure the impact of preschools in Morocco in the short, medium and long term. To do so, we set up a randomized controlled trial involving 160 douars that were randomly selected from a large set of rural douars.