IMHO, given the incredible lack of maturity of the student body in general, I remember as both a student and TA, I'm inclined to agree with the "No knives or weapons for students". OTOH, I think that if you can be trusted to effectively raise our kids, then you should be able to be trusted with a sharp tool.
Maybe with today's kids, but we all had knives in school and I graduated in 91. Kids threw punches at each other (one girl took down a teacher one time as well) but their knives always stayed in their pockets.
Bragging how everybody got into fights, but nobody got knifed is not a very convincing argument for maturity. Dropping a teacher is an even less convincing argument.
And, yes I know the difference between rough housing among friends and putting somebody, namely me, in the ER.
EDIT: OTOH, I don't remember many people getting knifed. I did lose a couple of classmates to gunfire though...