A "buff boy" is typically a male who is muscular. "Back of of class crew" is usually the group of troublemakers. "No notion" means no motivation. "Pervs" is internet slang for perverts. A "bunker" is someone who skips class or work.

In my world "no notion" means they do not know. He has no notion that he is about to get dumped. He has no notion about any of the chemistry we are supposed to know.