Oh God, I remember being in school. Here's how to get them back:
Buy a unique flavor of chips they have never heard of (try Dragon Sweet Chili Takis) in bulk.
In plain sight of those who excluded you, pass out your new chips to everybody except for them (covertly so as to not draw attention from the lunch monitor). Say nothing.
If and/or when asked by the lunch monitor, say that the chips were probably brought in by someone else and you have nothing to do with them.
