Some kids can sleep through anything. One guy fell asleep while we were watching Frozen in Spanish in my Spanish class. Señora turned up the volume, turned it way down, then paused it. She had to shake him awake.
That's one account. If he was really shouting, he'd be paying attention. If he wasn't listening, how would he know that the teacher was talking to him?
http://media.tumblr.com/4f957dc360c6471b3c684d9a7db55e0e/tumblr_inline_mgg5v5FCUb1qki93w.png