A framework based on research on bullying and on educational effectiveness was offered to schools to assist them in developing strategies and actions to improve their learning environment, their policy for teaching, and their evaluation mechanisms in order to reduce bullying. At the beginning and end of the intervention, the Revised Olweus Bully/Victim Questionnaire and a teacher questionnaire measuring three school factors (school policy for teaching, school learning environment, and school evaluation) were administered to the experimental and control groups. This experimental study reveals that the intervention had both a direct impact on the reduction of bullying and an indirect impact through improving the school factors. Implications for research into supporting schools to reduce bullying are given.