Objective Though many studies have found that teenagers overestimate their chances of college completion, the sources of this bias are still not well understood. Methods This article compares individuals' college expectations as teenagers with their subsequent college outcomes using data from the 1997 National Longitudinal Survey of Youth (NLSY97). I analyze how a rich set of youth characteristics correlate with the discrepancy between expectations and realizations. Results Teenagers' expectations are highly predictive of future college completion, but they are also systematically positively biased (overly optimistic). I find that scholastic aptitude—as proxied by youths' AFQT scores—is highly negatively correlated with expectation bias. Once test scores are accounted for, family income, parental education, race/ethnicity, and sex have little or no effect on bias in teenagers' college expectations. Conclusions The relationship between scholastic aptitude and college success may not be well understood by some youths, contributing to inflated expectations among those with lower test scores.