This study evaluated the effectiveness of an intervention in improving the general, academic, physical and social self-concepts of 2nd to 6th grade students. The activities were carried out by the teachers during the 1992-93 school year. A questionnaire was completed by 271 students of the experimental school and by 467 students of the control school, both before and after the intervention. The multiple regression analyses showed important adjusted gains for self-concepts related to physical appearance, mathematics and relationship with parents. In all three cases, students with the largest deficit benefitted most from the intervention. This study shows that it is possible to improve self-concept and to do so through an intervention carried out in the school environment. This double finding is important to the promotion of psycho-social adaptation since self-concept is an important determinant and since few interventions have reached similar objectives.