It is often claimed that the one-teacher, one-room, non-formal school model is more effective than the formal school in enrolling hard-to-reach children. This model is, however, not immune to the two-fold challenges of primary completion and transition. This article draws on data from three rounds of surveys with children from "Tsangaya" (traditional Quranic schools) in northern Nigeria who took part in a non-formal school programme. The article records project success in attracting children from "Tsangaya" schools and enabling them to complete the primary cycle. It shows that students' innate abilities and mother's education and income-generation ability seem to have a bearing on retention in primary school, while quality of teaching has an association with primary completion. However, it records major challenges to the transition to secondary school and argues for recognising the distinct challenges to primary completion and to transition from primary to secondary education.