I know what you are trying to say. I was whispering to myself the entire episode, “Dont do anything crazy! You’re not a cop anymore!”.
I think he realizes now that every time he has tried to be a hard-ass cop or go wild has got him nothing but trouble. Prez being Prez has netted him nothing.
Also I think he realizes that he is truly flying solo now. He has no father-in-law who can protect him. There is no ‘Wall of Blue’ that give him the benefit of the doubt if he does something well-intentioned but disasterous.
Also the racial aspect. I would have loved to see Prez give at least one of those kids a well deserved slap in the back of the head, but in that sense he has less options than any other new teacher. He left the police force under a racial cloud. He shot a black undercover officer, and some felt Prez was too quick to fire on a black person with a gun. So if he had thrown a desk, it wouldn’t have been viewed as an inexperienced teacher losing it. It would have been viewed as that guy who doesn’t like black people terrorizing the kids.