Conversely, high school and older students can be taught to respect social distancing, mask wearing, etc. (Doesn't mean teens will listen, but they at least have the capability). Good luck telling younger kids to stay 6 feet away from each other.
Things like chorus simply can't happen. At least not a big chorus. Good bye assemblies. Phys Ed limited to outdoors, distanced, non-contact activities.
As for regular classes... limiting class size, using the largest possible rooms. Limit cross-grade mixing.
Maybe the hardest aspect is transportation for areas that rely heavily on busing. I guess strongly encourage drop-offs, increase the number of buses with fewer kids per bus.
No matter what, it's going to be a real challenge.
Look at it this way, if Harvard and Princeton don't think they can keep their full student body safe, what are the odds of Valley Elementary School really being able to keep everyone safe?
With infection numbers exploding in early July... what are the chances of infections being low enough in late August, whereby hundreds or thousands of students will be entering a school building... what are the odds that you can avoid any infected individuals from entering the school?