I'm not sure what the current school day is. Would making the SSD 8:30-3:30 and the EASSD 9:30-4:30 fix the bus issue?
It'd make it less bad but a school bus could still not pick up 3 separate grade levels at once.
Also one thing to keep in mind is some rural school districts (including a few in rural Nevada) do 4 day school days and make each school day longer (by 60-70 mins or so) so with a strict start and end time, that'd no longer be possible.
One more feasible remedy is prohibiting the school day from starting say earlier than 8AM and not bothering to legislate the end time.