An English class a few years ago. It was quite long and uneventful, although by nature I actually enjoy English classes and grin like an idiot over new vocab; but during that class in particular as soon as the teacher said, "Ok, take a 5 minute break," I put my head over my table and drifted off to sleep. The teacher didn't really say anything, I think I was considered one of the "good ones" but she did tell the person next to me to wake me up.