ok, here it is...
you and a bunch of friends all bring in like 5 paintballs...or someone bring in a big bag, and everyone meets in the morning and takes some.
the more people you get to do it, the better.
pick a certain time, say between 2nd and 3rd block, and as everyone's walking through the hallways, just drop one at a time, so in the hustle and bustle, kids can't see who dropped them.
have a lot of people do it, so they're all over the school.
laugh.