I saw a news story on Fark recently where a mother came on the bus and slapped her son's bully in the mouth. She went to jail. The ensuing discussion by everyone had MANY tales of people either telling their kids or being told by their parents "If a bully starts shit with you, do not ever start a fight. But if a bully physically assaults you or starts a fight, you make damn sure that YOU are the one who ends the fight and that YOU are the one who walks away from it." Expecially if it's routine, there will be enough other people to back the bullied up in saying "He had enough". That bully will move on to weaker targets. Bullies do not like targets who fight back and stand up for themselves.
Of course nowadays, if you DO stand up for yourself, YOU are the one who gets thrown out of school and the bully gets next to no consequences and his bullying behavior is reinforced. Makes me sick.