I know I read a study a few years back about how lack of sleep is a problem as well as the cycle of a (teen in that study) is such that they need to sleep later. It's how they are set. That they did much better in school when it started later.

Here, my daughter is out the door a bit after seven. Ted is next at 7:45, Fin at 8:35.

Fin's school is interesting, they have different hours, all downtown schools do, they end late every day but Wednesday, and Wednesday is a half day so teachers can work on the special training they need to work with the community (it's a poor area).