You are correct about the other things as weapons part, but we gotta start someplace. In a controlled environment like a school, in todays world you have to have a hard and fast rule, in this case NO KNIVES. There are already rules (laws) about cutting people up, but given the world we live in today, a "knife for cutting food is OK, but don't bring one to cut classmates" rule just won't work...
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OBG