The present study examined the therapeutic factors operating during a psychoeducational group intervention designed to promote school adjustment in first-grade students. The group members completed the Critical Incidents Questionnaire at home after every group session. The therapeutic factors were classified according to Bloch, Reibstein, Crouch, Holroyd, and Themen’s taxonomy, although additional categories of critical incidents were applied. Results showed that guidance and acceptance were the most valued therapeutic factors. Cognitive factors were reported more often than behavioral or emotional ones. In addition, the presence of the therapeutic factors was more intense during the beginning and middle stage of the program, gradually giving their place to other categories of critical incidents. Overall, the emergence of therapeutic factors appears to be affected by the program’s educational aspect. We suggest that a wider classification of factors is required to reflect the variety of critical incidents occurring during a psychoeducational group intervention.