I do the same thing too, performing at school. With me, it's been better because I started performing at school about 7 years ago(when I started magic) and still continually perform today. What works for me is setting the precedent before you even start. I usually don't perform until someone says "Oh man, this guy is great at card tricks. Can you do one? Hey guys, check this guy out!" Once the audience wants to see the trick, much of the time they don't want to ruin the magic by figuring it out. Crowd control with hecklers is a bit more difficult, but what I do is say "But wait, hold up for a sec, watch this" and I just move on with the trick to something so mind-blowing, hecklers won't even know how to react. At school, let your audience choose for you to perform and then go for it. I think that's the safest way to do it. In public, that's all for the magician's choice. Basically what I'm saying is performing at school is difficult, but if you're careful and go about it the right way(and there's multiple right ways) it could be definitely beneficial. (And you should always have backup plans, like you do with your extra decks
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