The correct answer is their. Because his or her wouldn't make sense because it says they, his also wouldn't make sense for that reason, and the other form of there means for example, "over there"
YES! The current schedule messes with teens sleep patterns. Teens get tired at 11pm. So if 1st period starts at 7am thats not enough sleep. Yet younger kids, (more awake in mornings) have later start times.