Refers to a beating often severe or even deadly inflicted on a person by another, esp. a outlaw biker. One who says or does something insulting or threatening to a biker will probably be educated, meaning he has learned, hopefully, to not be stupid and cop an attitude around a patch wearing biker. Often it is a drunk guy in a party or bar who thinks he can beat the biker in a fight. Maybe he can but if he does he will be educated later by the rest of the club, hence the saying "one on all, all on one".
A friend asks another about his black eyes, missing teeth and stitched up face. The friend says he hit on a biker's old lady at a party and the biker became angry and educated him, teaching him that it was the wrong thing to have done. He has learned that bikers don't suffer fools in their midst. The price of "stupid" is steep.