This study examined mathematics anxiety among high and low achieving students (N = 237, grades 9 and 10) by contrasting trait (habitual) and state (momentary) assessments of anxiety. Previous studies have found that trait anxiety measures are typically rated higher than state measures. Furthermore, the academic self-concept has been identified to play a moderating role in the trait-state discrepancy, with higher academic self-concept leading to a lower discrepancy (i.e. less overestimation of trait anxiety if state assessments reflect actual experience). Therefore, we assumed that high achievers who were expected to have high academic self-concepts would exhibit a smaller trait-state discrepancy than low achievers. Results confirmed these assumptions and revealed that high achievers even underestimated their trait anxiety. Implications are discussed.