Summary.The aim of the present study was to explain the relationship between expectancy and subsequent academic achievement. A modified version of effort calculation theory was used to generate hypotheses regarding determinants and effects of expectancy in the academic achievement situation. The hypothesis that past achievement, work spent in examination preparations, and perceived ability determine both expectancy and later examination performance, and thereby account for the relationship between the latter two variables, did not find support. With preparation work, past grades, and perceived ability controlled, expectancy still related to subsequent grades. The hypothesis that expectancy determines effort expenditure in the examination situation, and thereby grades, was also not supported. It was suggested that expectancy as an expression of self‐confidence might be more strongly related to style of working in an exam situation than to an energy dimension like effort expenditur