This is so the older kids can start earlier. There are only so many buses. Adjust one to start later and the other starts earlier, and vice-versa. The high schools should have the 9:00 start and the elementaries should get their 7:40 start or whatever it is, assuming the whole window can't be adjusted.
Nb. I've had it explained to my by people in education that early starts in high school are insisted upon by the sports folks, so they can have longer afternoon practices with sunlight in the Winter, and that there's no hope of switching start times up on a large scale without attacking that constituency and winning, which is... probably not gonna happen.
But you're right that part of the problem was that there was no interest in spending more on transportation (or in generally improving the poor state of transportation). I'd say it's also worth questioning why we insist that all students need to go to school at the same time. The education system seems needlessly rigid (though I suppose imposing a certain amount of conformity is one of its goals).
What is this, the ski team? No popular USA scholastic winter sport takes place outside. (It's cold outside in winter!) Indoors we have artificial lights. In my experience, high school basketball teams regularly practice in the morning before school anyway; they would not complain about that starting at 7:30 rather than 6:00 AM.
[citation needed]