Only a few studies have examined the direction of associations between academic achievement, interest, and self-concept of ability simultaneously by using longitudinal data over several school years. To examine the cross-lagged relationships between students' interest, self-concept of ability, and performance in mathematics and reading, longitudinal data from Grade 1 to Grade 7 of comprehensive school was gathered from 216 students. The results showed that, in both reading and math, performance predicted students' subsequent self-concept of ability. Some evidence was also found that math performance predicts subsequent interest in mathematics, and that self-concept of math ability mediates the impact of math performance on interest. No evidence was found for the assumption that self-concept of ability or interest would predict subsequent academic performance.