In the middle of the 20th century, there was a shift from a skills deficit approach to a positive approach, focused on promoting assets and individual strengths. The role of social-emotional competences became salient. School is a privileged arena for universal and selective prevention interventions that can help pupils in raising their competence to cope with life challenges in a relaxed, non-violent and effective way. Personal and social-emotional skills play a key role in children and adolescents' development, as well as their behavior towards risk factors and there is a need to evidence-based interventions. The scale "For me it's Easy" is an evaluation tool for personal and socio-emotional skills and was used to assess the effect of a Social and Emotional Skills Promotion Program. Personal and social skills play a key role in children and adolescents' development, as well as their behavior towards risk factors. The study includes an intervention group with 960 Portuguese children and adolescents with a mean age of 12.5 years (SD = 1.61) and included were 56.8% boys of different educational levels. The waiting-list group included 171 children and adolescents; 46.2% were boys. The mean age was 14.7 years and the SD was 3.3. The results reveal significant differences in the intervention group related to the competences before and after the intervention, namely in the interpersonal relationships and definition of goal related skills, while in the waiting list group there were no significant differences in the moment before and after the intervention, and the scale "For me it's Easy" can be considered an instrument which contributes to the research and evaluation of intervention in children and adolescents, especially in the prevention and promotion of personal and social skills and healthy development.