This chapter focuses on bullying in schools and draws on research from both developmental and organizational perspectives. It demonstrates that by working on the whole school system, bullying not only decreases but, in a parallel process, "bullies" as well as "victims" receive support. Research typically examines characteristics of bullies and victims and offers explanations that draw on theories of, among others, aggression and personality. Only bullies, victims, and uninvolved children participated. The results showed, once again, that bullies often had no biological father at home. Children are not bullies or victims in the same way as they are blond or brown. Children have bullying or passive behaviours that make them act the role of bully or victim within a group. The intervention is to reinforce positive alternative relational strategies and behaviours, more pro-social and cooperative to those that all pupils, bullies, bystanders, and sometimes even victims are used to.