Initial access to school is nearly universal in Kenya, but many children who enroll drop out before completing primary school. In this mixed-methods study, we use quantitative data from a randomized control trial involving 2666 upper primary-grade students, as well as qualitative data from interviews with 41 schoolchildren, dropouts, and parents, to examine dropout. Poorer baseline performance on literacy and numeracy assessments predicted a higher risk of dropout. Interviews revealed that children are the primary decision-makers rather than parents. Together, these findings suggest that school quality interventions may be an effective means of reducing primary school dropout in this region.