Hörsch et al. (2026) developed the COMPASS intervention to foster students’ subject-specific self-concepts by addressing dimensional and temporal comparisons (i.e., comparisons of one’s own performance across subjects and with one’s own past performance) and related beliefs (positive interdependence between mathematical and verbal abilities and changeability of abilities). An assessment conducted immediately after the intervention showed that this intervention was effective in enhancing students’ math and English self-concepts. In the present study, we examined whether these findings could be replicated for a separate waiting-list control group within the same project. Moreover, we tested the long-term effectiveness of the intervention using three-month and six-month follow-ups. A total of N = 600 students (Grades 9 to 11) from German secondary schools (academic track) were assigned to two groups. Group A took part in the intervention between the first and second measurement point, with follow-up assessments after three and six months. Group B (waiting-list group) took part in the intervention between the second and third measurement point, with a three-month follow-up. Baseline change models indicated increases in students’ math self-concept and related beliefs at the immediate post-intervention assessment in both groups, and increases at the follow-ups, particularly in Group A. The effectiveness of the English intervention was demonstrated in Group A immediately after the intervention and at the follow-up assessments. Overall, these results indicate that the COMPASS intervention can sustainably improve students’ math self-concepts and highlight the potential of dealing with comparisons and comparison-related beliefs for the effective promotion of students’ self-concepts.
