STAGE 3. Intervention. Note: simultaneous activities in both groups. STAGE 4. Evaluation 2 (at the end of the intervention). Application of questionnaires in control group and intervention group. Anthropometric measures taken to control group and intervention group. Delivery of results to students and parents of both groups. STAGE 5. Evaluation 3 (three months after evaluation 2). Application of questionnaires in control group and intervention group. Anthropometric measures taken to control group and intervention group. Delivery of results to students and parents of both groups. Delivery of report of global results to executives of the educational institution.