This troper once fell asleep for a little while in his high school physics class. The teacher noticed, and when I woke up (couldn't tell why; maybe someone poked me or the teacher called my name and my subconscious picked up on it) it seemed like the whole class was looking at me. Oddly enough, I've actually been sleepier in college without falling asleep, probably because being sleepy more often made me learn ways to stop myself from falling asleep, like chewing gum...