Some schools around here are going to be starting off with online learning or even doing the whole semester online, while others are starting off with in person learning or the hybrid model. This will create a live experiment of sorts, although kids have friends and get together with kids who live in other towns which will still result in a lot of mixing.
I don't pretend to have all the answers, but I'm not sure about the hybrid model of kids going to school in person for 2 or 3 days a week and staying at home for the other 2 or 3 days. There is still about 6-8 hours of possible exposure on the days they are there in person.
Holding classes outdoors seems like a decent idea just from a virus standpoint, though I imagine it would be easier for kids to become distracted outdoors and you could only do that for so long in many parts of the country.