I am guessing it is because of buses; the same bus has to take the highschool kids and the elementary kids. It used to be the highschool kids went first, and then the elementary school kids.. now they are reversing it, so the younger kids have to get up earlier.
The same set of buses is used for elementary, middle, and high schools, so elementary schools in most places tend to start later (like 9am) and the high schools earlier (like 730). The district in the article probably just reversed those times.
Because they use the same school buses for elementary high school, but not at the same time. The routes are based on where the students actually are, so combining them would make transit time significantly longer for each student, plus I'm sure there are other concerns about having rowdy teenagers on the same buses as kindergarten students.
They shifted the bus schedule to better accommodate the older kids which means the younger kids had to catch a bus over an hour earlier. My point is "all kids" drag ass in the morning, but IMHO teenagers are better equipped to deal with it than a child under the age of 10.
Actually if you read the research it disagrees with you.
Younger kids naturally rise earlier than teenagers. You can talk as much as you want about "they should do this" and "understand that", but you can't fight their basic biology.