This chapter presents the main results of a peer aggression and well-being study conducted with a total of 535 Spanish schoolchildren aged 12 to 16 years who were in the Compulsory Secondary Education (ESO) stage in the Spanish education system. The academic calendar and timetable in the ESO are fixed by the autonomous community. The autonomous communities regulate schools in the management of bullying through specific orders whose objective is violence prevention and the promotion of convivencia in schools. A resolution of September 26, 2007 resulted in mandatory measures that stated schools must follow an action protocol in bullying, mistreatment, or discrimination cases. The prevention of bullying and the promotion of school co-existence in the community of Andalusia are part of the action protocol called “School: Spaces of Peace”, approved in 2007. A higher number of victims of bullying were observed in Grade seven, which is the first year of the Spanish secondary school system.