A large body of work in educational economics displays the tenuous relationship between school inputs and cognitive achievement. Among others, the inability to establish a strong link has been attributed to the difficulty of controlling for attributes such as ability, motivation, and interest. Against this background, and inspired by work in economics and educational psychology, the authors examine whether a child's interest in school has a bearing on educational success. The panel data estimates, based on Portuguese data, show that after controlling for socioeconomic background, school inputs, and time-invariant unobservable traits, children with high levels of interest are 6-10 percentage points less likely to fail as compared with children with low and medium levels of interest.