thank you so much! but what if I said this person would wrestle you to the ground trying to figure out the trick?
How young are you and this kid?
Anyway, unless you are talking about assault, who cares. If he figures out the trick this way, so what? Don't ever, ever, ever, show a trick to this person ever again. If this is at school, you have to be patient and don't show tricks when he is around. If this means that you don't show tricks for a few weeks then live with it. If other people want to see your tricks and they realize that you are not going to show the tricks with this jerk around, then they may help you to stop the heckler/assaulter. Peer pressure is a wondrous force.
But remember that your audience may not be sure which "show" to watch--the magic show or the "heckler" show. Make sure they want to watch you and not the heckler. It may take time to become the headliner.