We study the impact of delayed school entry on the locus of control (LoC) among Hungarian students, using statutory cutoff dates for school enrollment as a plausibly exogenous variation. Our findings indicate a causal relationship between delayed school entry and an increase in internal LoC, with a policy effect of approximately one-tenth of a standard deviation for 8th-grade students, which corresponds to a one-third standard deviation effect for complier students. The policy implications of these findings are significant, providing evidence that delaying school start could serve as an effective intervention to enhance LoC among students, which is positively associated with many later life outcomes.