A participative research-action was carried out at the “Colegio General Santander de Chia” on 32 children of school age showing aggressive behavior, in order to watch how both family and school environments influence aggressiveness and suggest alternatives leading to modulate such conducts. The study inquired, among parents and children, certain conclusive factors contributing to trigger hostility. An evaluation was made of family structures and people responsible for the care of the children; their dwelling conditions and other factors were assessed, such as parents’ education level and employment situation, corrective methods, overcrowding, and consumption of alcohol by parents, adults and childminders in charge, as determining variables of the family environment. It was found in this case that the main causes influencing the children’s bellicose manifestations were the particular type of their family structure, the low schooling level of both their parents and other people responsible for their education and care; and the school environment as a source of imitation of aggressive conducts.