Teacher absenteeism and shirking are common problems in developing countries. While monitoring teachers should ameliorate those problems, mobilizing parents to do so often leads to small or even negative effects on learning outcomes. This paper provides causal evidence that this might result from non-monotonic effects of monitoring teachers. Cross-randomizing nudges to teachers and parents in Ivory Coast - to motivate and monitor teachers directly, and to mobilize parents -, we find that in schools where either parents or teachers are nudged, student dropouts decrease by nearly 50%. In contrast, in schools where both are nudged, there is no effect on dropouts.