Stop and searches plus punishment* for carrying offensive weapons might be a starting point.
I remember Paul Sheader producing a 12 inch? Bread knife at school. He was swiftly dealt with. Knife taken off him. Marched to heads office and after a wait, a good caning. Then suspended and parents had to plead for him to be able to return.
Contrast that with my good friend who gave up teaching following a string of incidents. The last one. A kid had dribbled water into a socket and then was trying to force another child’s fingers into it. He called him a “ stupid boy” and dragged them both away. Later in the afternoon he was called into the heads office where both parents were present with the offender. “ Did you call this boy stupid?” Well he was… “ No, did you call him stupid? Yes. “ We don’t call pupils stupid, apologise now.
* For the parents too. I don’t care what anybody says, most of societies problems today can be laid at the parents door. Crap parenting.