If school starts at 7:30, then that kid isn't waking up fresh at 7, they have to be woken up significantly earlier. I shudder to think of the other examples in the comments which have to already be in school at 7.
But sure if they are put to bed at 9-10 then its going to be tougher.
The moment I got into university and could move my schedule my GPA went up two grades.
8pm bedtime is great with no other obligations, but I was regularly at school events past then (lacrosse games, robotics, quiz bowl, etc.), so that schedule would have prevented me from doing a lot of things I enjoyed in high school
So they have plenty of obligations we are just very strict with when they go to bed which means that in general we don't have an issue with getting them to sleep.
Putting the kids to sleep at 8 doesn't mean going to bed at 8pm myself.
Again we keep a strict schedule. Dinner at 6, bedtime reading at 7.30, light out at 8.00.
Weekends we are a little less strict yet they normally wake up at 6 anyway because they are used to it.
All it requires is the same kind of prioritization and effort we put into so many other things we care about.
Depending on the school district 7am start times means busses are going to start their pickups much earlier, sometimes as early as 6am for some students.