The primary to secondary school transition is the first bottleneck in educational trajectories worldwide, resulting in low secondary school completion. This study aims to determine if and how an educational program to promote transitions from primary to secondary schools, as implemented in Uruguayan schools, impacts these transitions to secondary education of Uruguayan children, in particular of those with low socio-economic backgrounds. The methodology includes three studies: an impact evaluation of the program and its different implementation modalities, a longitudinal follow-up through administrative registers of the educational trajectories of a large students‘ cohort and an in-depth qualitative study to assess the particular program elements leading to possible impact.