The assumption is that the teenagers are falling asleep because they are bored or disinterested in the class. Was elementary school more exciting than high school? No, that is not the reason. It is a misconception that boredom causes sleepiness. Boredom just unmasks sleep deprivation.
Suppose after several days you're still having trouble settling down to sleep at the earlier time and you're dragging yourself slowly throughout the day. Here are a couple of suggestions to advance your sleep clock.