Lol. Thats going in the sig. And on topic the way to deal with it, as others have said, is simply not to play in school. I don't so i never have a problem with this sort of thing.
i don't honestly think that is the answer. i think that that just postpones the problem and breeds into the hobby an atmosphere that says its supposed to be mocked (and only those deserving of mockery should play).
i also think that there has been a lot of very bad advice handed out in this thread. clearly threats of violence and attempts at offence are only going land you in even greater piles of mockery. the solution to the problem will never be trying to exclude people.
the real solution is trying to get everyone involved at a level they can cope with. younger players don't need to be 'playing the game' if all they are interested in is the miniatures, and curious on lookers should be introduced positively, not scowled at because they don't smell and have crap facial hair.
of course on lookers are always going to be able to mock you, but if you have a good group of friends that always have fun when they get together, there are going to be far more people that want a piece of the action than people who want a piece of you.