Why assume there is a rational explanation?
Jason, the ringleader, is a sociopathic narcissist who lacks any moral compass or empathy for others. It is all about him and his ego. He lies freely (as in his false claim to Ross that they weren't going to do anything to Perry) when it suits his purposes, and would not understand why anyone would see anything wrong with that. Perry is a challenge to his ego, and must be dealt with. There is no logic to it. Inflicting pain or discomfort nourishes Jason. He will grow up to be a career criminal or a politician.
Dante, as far as I can tell, is just a thug who gets off on acting as Jason's enforcer. I doubt if he has had an original thought in his life.
Adam is just an idiot who has never had to face real consequences for his irresponsible actions and loyalties. Which I suppose is another way of stating that he is very immature.
There is no hope for Jason, and probably none for Dante either. They don't belong at that school. The others are probably salvageable with proper guidance.
R