They want to start elementary school at basically 10am? I am screaming this is WILD.
No, Scenario C2 as the OP pointed out has MIDDLE SCHOOL starting at 9:40 and ending at 4:25. Elementary Schools would run 8a - 2:45 or 9:10 - 3:55, and HS 8:30-3:15.
I'm gonna say that this will completely throw a wrench in after school activities for that age group. You're going to have them getting home at 5pm, and then activities running 7-9? 7:30 - 9:30? I feel like this is just going to push 12 and 13yo kids to go to bed even later because they go to school later, which is counter to the entire point of this exercise.
At this point, just leave it like it is and shuffle through the 2 years of Middle School with the early wake up/rise. Yikes.