Research on the self-regulatory implications of psychological control suggests that overestimations of one's capabilities may be associated with enhanced performance. We examined this hypothesis in a two-year (three-occasion) longitudinal study of 381 German school children (8-11 years of age). Controlling for gender, grade in school, prior academic achievement, and level of intelligence, we used path analysis to examine the longitudinal relations between overestimations of one's personal agency and subsequent school performance. We expected overestimations of one's agency to facilitate subsequent school performance. Furthermore, we expected that this relationship would be strongest for those with moderate overestimations of their agency. Supporting our first hypothesis, overestimations of one's capabilities were consistently associated with improvements in subsequent school performance. However, our second hypothesis was not supported. The results suggest that overestimating personal agency is one possible mechanism through which one maintains and improves performance.