It's extremely likely that nobody wants to rock the boat and give an injured party evidence to be used against their employer. Their employer would almost certainly prefer to wrongly punish a student if it has a fraction of a chance at getting them out of a lawsuit.

It's also likely that there isn't a single person in a leadership position with the entire school board who is even slightly technically competent.

Next we already have precedent that IP addresses don't uniquely identify people for the purposes of law. It is incredibly likely that such an action wouldn't pass the sniff test if the IP addresses given were entirely correct.

Lastly even if he actually did try to log in with "i will murder u all of u" no reasonable person would consider this an actual threat without talking with the student. Kids are stupid, and kids say stupid things. Time and again schools fail to address the real problem children before things blow up and then use their persistent failures to justify overreaction to the detriment of students.