with the right, and correct safety gear you may get a couple of scr***es and brusies, i think someone managed to break their little finger with wrist guards on, thats about as bad as it can get, if as sprog said your in a correct environment, and not trying to do flips say on your first time on them.
with out pads, you can break your wrists, but i figure seen as your getting them for christmas and your mom has a say in it, your only young, so you should make sure you are fully padded up and if your gonna try anything stupid make sure your around other bockers who know what can go wrong, and what to do if it does.
but in short Bocking is a dangerous as the person on the stilts, i touch of common sense and the correct padding and you should be like robo bocker, unbreakable.