@FgoSegul How do you envision that? Even if he had the stomach to kill his parents or his brother, that'd be a crime making him lawless and hunted by all (state bounty on his head kind), supported by the new head of the territory (since he might still have some vague legal claim to it that someone else could abuse later, c.f. Lex Crusader Kings).
And if he doesn't go all out killing them, they probably won't send any troops after him either, but they will be financing troubles for him until he's moved so far away that everyone thinks he's dead. (Can't rent an apartment because they pull in favor with the landlords boss, can't get a job other than a mercenary.. it's nothing that would kill him, but it's the kind of pesky annoyances he didn't want.
@OddOwl It's mostly extortion, but his OP ain't more than that of a gunslinger. So like Doc Holiday he realizes that if he doesn't go with the law, he'll get set up against it. And he can't shoot himself out of an expulsion. (It's more like, if he tries to kill the student council, that'll only make his expulsion all the faster, and probably end up with jailtime).