Answer:
Students often get less sleep than needed.
Step-by-step explanation:
It starts the topic off by saying that highschool students have busy lives by saying "High school students are busy juggling responsibilities and fun". Then it switches subjects to the fact that teenagers go to bed late and wake up early, that is the main topic wile everything else they talk about in the paragraph are sub-topics (topics that are very related to the main topic) like explaining how your body grows with the required sleep, and stating facts about kids who don't get the required sleep
I hope this helps :)