This study focuses on third grade pupils' (9 to 10 years old) ability to predict their performance in a given task and on the correspondence between the accuracy and adequacy of the predictions on the one hand, and the academic achievement on the other. The study involved 713 pupils from 29 Estonian schools. The pupils' performance predictions about a short-term memory recognition task and their actual scores were used to specify differences in prediction errors and the correspondence of these errors with academic achievement. In line with earlier research, the results indicate that low performers often overestimated themselves and their predictions tended to be most inaccurate, whereas high performers were more accurate although they often underestimated their performance. Pupils with lower academic achievement often provided extensive overestimations of the memory task. Underestimations, together with better accuracy, characterised children with a higher achievement level. This can indicate a meaningful accord between specific prediction errors and broader achievement at school.