This research is a preliminary evaluation study to determine whether group counselling based on schema therapy has an effect on academic expectation stress in high school students. In this study, a 2 × 3 split-plot design was used. The Academic Expectation Stress Inventory was applied for data collection purposes. The effect of group counselling based on schema therapy on academic expectation stress was tested using a two-factor ANOVA for mixed measurements. As a result of the analysis, the intervention*time effect was found to be significant with regard to academic expectation stress. The findings obtained in the study reveal that group counselling based on schema therapy creates a significant decrease in adolescents’ academic expectation stress level, and this decline continues, as shown in the follow-up test. As a result, it can be said that the group counselling programme based on schema therapy, which was developed as a preliminary evaluation study, has the potential to reduce the academic expectation stress level of high school students.