The first reason school does not needs to start early is economy.For example, is would cost lots of money.“ it would have cost St. Paul $8 million to buy the needed busses” (www.achieve3000.com)
This means it is better to put the money into a classroom rather than a gas tank.
The second reason school does not needs to start early is safety.For example, some students do any after-school activities or have jobs where they spend most of the daylight