The present meta-analysis integrates results from 261 studies on students' expected and actual achievement. Cross-sectional and longitudinal studies found moderate, positive associations between expectations and achievement; the analysis of cross-lagged effects indicates that these associations were bidirectional. In addition, we found large differences between levels of expected and actual achievement, with expectations being more positive. The size of these differences slightly decreased over time. The effect sizes varied, in part, by age, ethnicity, socioeconomic status, kind of assessed expectations, matching of contents of expectations and achievement, and publication status. We conclude that available data support the perspective of informed optimism in that success expectations reflect, to some degree, past and future performance as well as hope for improving one's achievement.