according to the current handbook for my old highschool, criminal possession of a weapon is defined as "knowingly possessing or carrying, with intent to cause harm or threaten to cause harm, any weapon or potentially deadly object."
Key part of that is the "intent to harm or threaten" part. That means a reasonable person can decide the knife in your lunchbox, or the lone shell in your hunting jacket was not going to be used in a massacre and send you on your way. And if they think you WERE going to try and kill your peers with the Squirt on the keyring in your car, they have to prove that was your intent. The problems start when you make a Zero Tolerance Policy regarding ANYTHING. That leaves no room for reason. You break this rule and you're out, end of story, no questions asked.
I read stories like this and it just makes me more determined that I don't want to live in the city, cause that's where all these crazies seem to hang out. You never hear about a kid getting hauled away in handcuffs over a pocket knife in the rural south. Ask anyone down here and you'll get the same response: "Man, that's gotta be tha dumbest thing I ever heard. The ones who called the cops are the ones who aughta be arrested for wastin the officers time and terrorizin that poor kid."