Exactly what you described. Sounds like you have established a relationship with the student. I would say, “I’ll wait for you” & make sure you’re silent & don’t move until the kid has put it away. Otherwise, he’ll think you’re bluffing. If he refuses, I’d continue class & assign quick table practice to distract the kids. Then, I’d walk over to the kid and non-threateningly check in with him. Something like, “I see you’re not in the mood to do school” or “ it must be tough to be in school on such a gorgeous day” You get the kid talking, offer him to take a little break and get water, and you will have a better reaction than desk throwing, for sure. I don’t know anything about charters, but I would ask the admin if she anticipated triggering the student & potentially other kids in the room when she did that.