Your admin’s passivity is not surprising. When I was a high school teacher, admin would not intervene with any aggressive behavior if the student was privileged. I’m guessing they were afraid the parents would sue. If a student was a problem and wasn’t privileged, however, they would tell that student to go to another school. Two non privileged Black students of mine were more or less expelled during the time I taught there. Privilege is a free pass for all kinds of behavior. No doubt the student you describe here had some of that going on.