All school schedules historically are because of farmers and blue collar worker schedules.
Now that we’ve outlawed child labour (well, it’s coming back…) and your family’s survival doesn’t count on getting those crops picked, we now have freedom to choose school hours at any time. Those countries without such strong sports have had few issues moving it to later start. It’s the sporty ones that resist.
The poorer countries that still have mostly basic labour students and/or child labour are still on an early schedule for the same reason the more developed nations started out that way.
I’d say the only outlier is China. They start early and go loooooong. That’s for bashing in some of the best education at the expense of most other things. There’s probably a happy middle ground in there somewhere.