This paper provides novel insights into the science of scaling by examining an educational mentoring program in Mexico. The analysis encompasses two independent field experiments, and seizes a unique opportunity to learn from the government's implementation of the same intervention. While the program originally implemented at scale demonstrates limited effectiveness, the introduction of a new modality with enhanced mentor training significantly improves children's outcomes. Mentor-parent interactions are found to stimulate parental engagement at the community-school level, which emerges as a critical factor for the scalability of the program. Our findings offer compelling evidence on the socially determined drivers of education interventions at scale.