A six-year-old will not understand that By and large it has been demonstrated that violence is counterproductive to the constructive interaction of persons and societies. True. But a child can better understand that the rule out in the world and in the school is the same: Don't hit people. Bad things happen. The child must understand this rule is connected to the first rule: People won't share or play fair if you hit them.

All I Really Need to Know I Learned in Kindergarten (1986)