Research on the self-evaluation bias of students' school competence has focused mainly on its correlates for students' school adaptation. This study focused on teachers' theories about students with a positive or negative bias in their self-evaluation of competence. French students enrolled in the third and fifth grades of elementary school (sample 1, N = 508; sample 2, N = 322) and their teachers (sample 1, N = 27; sample 2, N = 13) participated in this study. We examined the relationship between the more or less biased perceptions that students have of their competence in French and mathematics and their teacher's judgment. Models for each sample were tested while controlling for students' performance, their gender, repeating of a school year, and average class level. The results for both samples showed that the more positively biased a student's evaluation of their competence was, the better their teacher's judgment was.