This paper evaluates the role that an after-school may play in the educational outcomes of children living in poor suburbs. Previous evaluations have focused on average effects, with mixed findings. A possible explanation of these inconclusive findings is that after-school programmes may have heterogeneous effects. Our hypothesis is that the impact of after-school programmes depends on parent type. Exploiting the existence of oversubscription for an after-school placed in the poorest region of a developing country, we design a randomized trial to assess the effects on academic achievement, behaviour, and grade retention at 1st grade in primary school. Employing an intention-to-treat approach, we find that the after-school programme under analysis is effective in raising children's school achievement for those with a "committed parent type." These results may be crucial for the designing of policy since increasing time in safe, supervised settings is not enough: The after-school programme demands parents' involvement.