Communicative and socio-emotional skills are associated with conflict resolution and, thus, school violence prevention. However, without using a combination of techniques in peaceful conflict resolution, it is difficult to ensure such a relationship. The present study aimed to evaluate the effectiveness of the FHaCE up! program, an intervention based on training in communication and socio-emotional skills, as well as conflict resolution, using a collaborative style and mediation skills to reduce school violence and improve the school climate. This training developed in two consecutive stages. The design of the study was quasi-experimental, in which 561 students (aged from 11 to 17 years) from two public secondary schools in Valencia, Spain, participated. Convenience sampling was assigned to the experimental group (N = 264) and the control group (N = 297). The results showed a significant improvement in school violence and school climate perception, as well as communication and socio-emotional skills, in the experimental group after the intervention implementation. It is concluded that the FHaCE up! program significantly positively affected teenagers’ perception of violence and school climate.