Andrea Westphal, Julia Kretschmann, Anna Gronostaj, Miriam Vock

• Students' achievement emotions are critical in their academic development. Therefore, teachers need to create an emotionally positive learning environment. In the light of this, the present study investigated the connection between students' enjoyment, anxiety, boredom and, in the first case, students' academic self-concept and, in the second, teachers' diagnostic skills. The third part of our study examined whether this link would be moderated by students' academic self-concept. Our sample comprised N = 1803 eighth-grade students who reported their achievement emotions and evaluated the diagnostic skills of both their German and mathematics teachers. Hierarchical models indicated that students experience more enjoyment and less anxiety and boredom if teachers exhibit better diagnostic skills. The role of teachers' diagnostic skills in relation to students' emotions was in part moderated by the students' self-concept. These results are discussed in terms of their implications for effective teaching.