About fifteen years ago one of my friends got suspended for bringing a knife in. He was going on a school trip and put his clothes in his camping backpack which always stored a small knife. The school searched the bags, looking for alcohol or something, and found the knife. The school had a zero tolerance policy, so no logic was applied.

I was really annoyed, so I cataloged all the knives already present in the school. I walked into the teachers break room (no one really noticed me): three kitchen knives on the drying rack. The wood shop had tons of sharp knife-like tools. Pointed scissors in the art room. A teacher noticed what I was doing and showed me the pen knife on their key chain. Most classrooms had a letter opener, box cutter, or similar at the teachers desk. I think I found thirty knives before I gave up.

Students need knives and sharp objects to learn. Controlling access is fine but eliminating knives if a fools errand.