The best way to deal with someone like this is to bust out an ungimmicked effect and blow his/her mind.
excellent advice: i've never been in this kind of situation, but here's my suggestion: the next time this kid does this, immediately stop what you're doing and say "wait... don't move".. then move a few steps away and do a balducci leviation. then just walk away (stumble, look sick, and run into a nearby bathroom). then, don't speak to those specs for at least two weeks. when you do see them, avoid eye contact in a mysterious way.
if you present the levitation properly, and have the correct persona going already, the heckler kid won't want to get near you, let alone heckle you. a well-performed balducci FREAKS PEOPLE OUT!!!
as a footnote, let me say that starting out in magic with gimmicks may not be the route to take. i would recommend learning sleight-of-hand magic, and perform that for a while. this will give you performance experience without the inherent risk of gimmicks.