If he is just starting high school, that puts him at 14. Assuming he isn't overweight I'd also assume then that he is pretty small? He would be fine tricking around on an old conversion. At 145lbs I was just fine learning to wheelie and spin around and slide around when I first got into fixed. After 3-4 months the fork started to bend from dropping hard on wheelies and such, but I just replaced that and was fine. Should he be jumping 10 stairs on it and trying to backflip, no. Will he be fine learning the ropes and messing around until he buys something more trick designed if he likes it, yes.