When Does EdTech Work? Evidence from a Scalable Home-Based Intervention with School Complementarity

Despite growing investment in education technology, evidence on how to integrate digital tools eectively into public education systems remains limited. Substituting classroom instruction with computer-aided learning has often failed to improve outcomes, even though schools remain the most direct route to scale educational innovations. This paper studies an alternative approach: delivering personalized educational software to households, where smartphone access is widespread, while experimentally varying school involvement. We evaluate Leo Leo, an adaptive early literacy app for young children, using a randomized controlled trial in 105 public schools in Nuevo León, Mexico. Schools were assigned to either (i) a family-only intervention providing access to the app, (ii) a combined family-and-school intervention that additionally provided teachers and principals with information on childrens progress, or (iii) a control group that received neither the app nor school support. The home-based technology generates robust gains in early literacy, with suggestive positive spillovers to early numeracy, when complemented by school support; the family-only intervention produces no signicant learning gains. Descriptive mechanism analyses are most consistent with greater child engagement with the software as the leading channel. We nd no indication that changes in parental inputs play a role, based on a household survey with a lower response than the student assessment. Overall, the results show that while home-based delivery of educational technology can enhance scalability, institutional involvement remains critical for translating scalable technology into learning gains.