To some extent, it would probably depend on my kid. ~9 is probably a good time to set for the bedtime though. Fridays and Saturdays would have a negotiable bedtime probably. I honestly can't remember what my bedtime was back then, but it was probably something similar.
If my kid is anything like me, he/she will probably stay up way too late anyways with a book and a flashlight. Maybe not at 10, but I know by middle school I would be up until after midnight quite frequently reading Harry Potter or whatever. There was some of that in high school, but I would often play video games I just got until something like 3am. I'd keep the volume on the tv low and listen for movement from the rest of the house to know if I need to quickly shut off the tv to avoid getting yelled at for being up. I'd be willing to be flexible to high school kids on a bedtime depending on the kid, though. If I have a kid who is suffering in school and what have you, I'd be more strict on bedtimes and whatnot.