This paper provides novel insights into the science of scaling by examining an educational mentoring program in Mexico. Our analysis encompasses two separate field experiments, and takes advantage of a unique opportunity to learn from the government's implementation of the program on a large scale. While the originally implemented program at scale demonstrates limited effectiveness, the introduction of a new modality with enhanced mentor training significantly improves children's outcomes. This improvement is observed in both the field experiment and the subsequent large-scale government adoption. We also find that the new program's enhanced mentor-parent interactions stimulate parental engagement at the community-school level, which emerges as a critical factor in facilitating the program's scalability.