The age old morning people versus evening people. Sounds like the kids aren't morning people either.
We should probably start high school later in the morning even if we stay on standard time ; it's way more important if we switch to permanent daylight time.
It starts earlier so it can end earlier so that there is time for sports and other extra-curricular activities?
Teachers spend time with students doing these activities, and the teachers have lives too. If high school ends at (e.g.) 2:30 pm, there's 60-90 minutes that stuff can happen and teachers still have 'regular work hours' of 8-4 (a shifted 9-5) so they can do things in their lives.
Activities also can stop during the really dark weeks around the solstice in a way school can't.
Don't necessarily disagree, just laying out a (possible) reason for early start/early finish.