Previous research has documented reliable effects of teachers' judgments or expectations, respectively, on their students' school performance. However, the importance of those effects has been controversially discussed because of their limited effect size. The impact of teacher judgments on students' lives might have been underestimated due to a neglect of student outcomes other than performance. The present study investigated the effects of teacher under-and overestimations on adolescents' school performance in math and reading, motivational constructs (ability self-concepts, intrinsic motivation, and educational aspirations), and subjective well-being. Participants were 1,092 ninth graders (522 girls; M age = 15.13, SD = 0.72), 52 math teachers, and 48 German (language of instruction) teachers. Teacher judgments uniquely and directly predicted developments over 1 year in performance (math: β = .12; reading: β = .16), ability self-concepts (β = .15; β = .08), aspirations for both school education (β = .12; β = .19) and vocational education (β = .08; β = .12), and life satisfaction in reading only (β = .03; β = .11). The significant effects were located at the student level, whereas there were no significant effects of teachers' general tendency to underestimate or overestimate their students. Both math and German teachers showed a tendency to overestimate their students on average. Underestimation had negative effects and overestimation had positive effects; most effects were linear. Results underscore the impact of teachers' judgments on adolescents' lives inside and outside school and illustrate the benefits of being overestimated and the downsides of being underestimated by teachers.
Educational Impact and Implications StatementTeachers' judgments of what their students are able to achieve have been documented to impact student performance, in the sense of a self-fulfilling prophecy. However, because those effects were mostly small, some researchers have disputed their practical importance. The present study documents unique direct effects of teacher judgments on math and reading performance, ability self-concepts, educational aspirations, and life satisfaction in reading only. The results also show that these effects encompass both negative effects of underestimation and positive effects of overestimation. Teacher judgments thus affect many student outcomes at the same time, underscoring their practical importance for students' lives. In addition, results suggest that overestimations, not accurate teacher judgments, are most conducive to adolescents' performance and socio-emotional development.