Sk8er boy wanna show off for buddies? Fine. He should rapidly learn to choose a better way.
Are they on drugs maybe? PCP? Meth? Personally, just to be safe, I'd advocate whackin' him back with a baton or sap, but that's just me. Taser would be just fine too. If someone, even in their low teens, walks up and hits me, well, I'm an old fat man... If I get in a fight, I'm going to be hurtin' for certain, maybe with debilitating long term injuries, or even dead. I'm going to use everything in my power to either get away, or take down my assailant. And take them down hard, so that I don't have to worry about a second try.