Of course everyone knows, but if the people who actually witness the offense aren't willing to come forward (because they think that the victim deserved it or b

Of course everyone knows, but if the people who actually witness the offense aren't willing to come forward (because they think that the victim deserved it or because they want to stand with a fellow student against Authority, or whatever), then standard disciplinary processes can't do anything. The analogous adult case is when a crime syndicate or a terrorist organization assassinates one of its enemies in broad daylight in the middle of a crowded street, and the police can't find anyone to testify that they witnessed the hit. If you don't change the priorities of the bystanders, you can't change anything else.