In recent years, the Chilean educational curriculum has reduced significantly the hours dedicated to musical, artistic, and humanities activities. However, research shows consistently that performing them enhances psychological processes relevant to the school context. This work provides the evaluation of intervention in music and humanities (MH) on the general self-efficacy (study 1) and qualifications (study 2) of students from different schools in the Maule Region. The first study shows that the intervention generates changes in the participants’ perception of efficacy, both over time and relative to a control group. The second study occurs after the activities and shows that participation leads to more favorable grades, mediated by self-efficacy. Results are discussed in curricular terms and the context of educational public policy.