Zero tolerance, zero brains
A 6 year old takes a cub scout camping tool to school and suspended because it includes a knife. Note also the third grader who was expelled after she brought a birthday cake and a knife to cut it (the teacher thoughtfully used it to cut the cake before reporting her to the principal).
UPDATE: I know an attorney here, a good friend, who had a mother come in and tell a tale of woe. Seems her kid had been fencing a stolen pistol at school. A potential buyer asked if it worked, and he showed it did by touching off a round in the air. On the school property. He got suspended or expelled, and the mother wanted to sue the school. On a theory, I guess, that is it utterly unreasonable to discipline a thief selling stolen guns, and shooting them, on school property.
The attorney yelled, get the hell out of my office! It's people like you and your little monster who make life hard for me and mine!