For teens, in this case a rising Junior in High School, is it appropriate to set a bedtime for him of 10PM? How does this compare with the majority of teens?
High school is a much better time to learn "how to go to bed on time" and "how much sleep you need" than your first year of college, university, or work. Therefore I recommend letting the teen work out when they want to go to sleep and get up. They will get this wrong a few times, and go to school groggy and exhausted, or miss a day of school, or not finish something that they wanted to finish. You can't and shouldn't protect them from these consequences.
What you can do is suggest a time for them to go to bed, 10 or 11 depending on when school starts and how they get there (the high school bus arrived at our driveway shortly before 7am, meaning a 6am wakeup to have time for shower, breakfast, packing a backpack etc.) Maybe even 9 if they are not getting enough sleep otherwise. When they stay up past it you can remind them what time it is. More importantly, in the morning, when they're feeling the consequences (they're tired, or rushed, or whatever) you can connect it to their choices the night before. And next time they're doing something late into the evening you can remind them about "last week when you played past midnight and felt so awful the next day."
The thing is, some things are way more important to teens than we know. Sure, homework is important, but band practice, gaming, and socializing are important too. Letting them set their priorities now gives them a chance for small failures with minor consequences. Making these choices for them throughout high school will mean the consequences are a lot larger once they start doing it themselves.
That said, you should not be kept awake by TV, video games, or music, and you shouldn't be leaving a 15 or 16 year old to talk to strangers on the internet all night. There is nothing wrong with mandated quiet time starting at 9pm, or an internet-off time of midnight. Just don't tell the teen when they have to sleep, or they won't get a chance to work out the learning process themselves.
At 16-17 I had no bedtime so long as I was home before legal curfew(where I lived curfew was 12 AM for anyone under 18 unless work related), went to school, passed my classes, and did my chores. This seemed to be pretty common because everyone I knew had the same rules. I think it works pretty good and is a more of a "real life" approach than having bed times. If they follow the laws and complete their obligations they get to choose their own schedule.
I'm a 14 year old boy and I'm pretty sure most people in 8th grade stay up past their bed times and just don't get caught. They stay up either because they do not want to be told what to do or want to show they can still be active the next day.
And I'm reading this at 11:30 and my bed time is 10 and I'm not tired at this time and the first time I stayed up like this I wasn't tired.
I think kids should not have bedtimes because it's a good way to show your parents you're responsible enough to wake up in time and go to bed at a reasonable time.
Maybe they have some late homework or some studying, I understand sometimes kids might stay up texting or on their phones or something like that or even TV, but if they don't wake up in time for school, it's on them.
But for kids that have to drive or bike, skateboard, scooter, I recommend going to bed early so you're awake when you're riding, driving!