There is a wide consensus that violence in schools is something so morally wrong that it must not be tolerated. Therefore, the intolerance shown by a teacher towards students' violent behaviour in school could be understood as a virtue and his moral obligation and legal duty. On the other hand, extreme toleration towards an evil such as violence becomes a vice, for example, when a teacher makes it possible for an innocent student to become a victim of other students' physical or verbal violence. It seems, therefore, that the idea of 'zero tolerance' policies is the right one, although the results of its application in practice have been many times problematic, inefficient and unjust.