Maurice, my school isn't a normal school. It is a lab school. My principal, and half the faculty carry Swiss Army Knives. They don't give me any trouble with Swiss Army classics and pocket pals (but I gave mine to my dad, so I needed to get something else).
The only time they really complained was when I walked in the office with my thumb bleeding all over the floor at which point they asked me why I had the knife (a cheap S&W SWAT). I told them I just brought it as a utility knife and they told me not to carry it anymore during school. No more questions were asked.
Three weeks later, I was carrying Schrade fixed blade openly on my belt, and I didn't even know it was there (I'm too used to carrying a knife and didn't even think about it when I left for school). All they did was ask me why I was carrying a knife. I said, "oops, sorry, didn't realize it was there" and took it off my belt and placed it on the office desk. Normally when I check in my knives they just let me pick it up after school, but since they discovered and had me check it in, they asked that I just talk to the assistant director. I told her that I didn't think about it and it was there without me really knowing of it's presence. No further questions, I walked out with my knife.
Also, there was the time when I was playing with a Jaguar balisong during history class. My teacher didn't seem to care and he just joked with me after class saying, "you never know when you might have to shave!". We've never had any problems with kids being stabbed, so no one is too uptight about it. The worst we had was someone flash his knife when he was argueing with someone. No threats or anything. He was suspended for a couple days, and it all stopped after that.
The official policy is no knives, not even pocket knives. No mention of multi tools and SAK's with non-knife attachments is made however. The faculty all carry them anyways on their key chains. Just be discrete about it and it is pretty much don't ask, don't tell unless the blade is a single bladed knife with a blade about 3"+.
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Chang the Asian Janitorial Apparatus