Colorado State University is currently beginning a study that's going to take about 3 months to run. They're using a bio facility meant for the kind of protocols that actually need to be done understand the actual impacts. Until we get the results from that study, and a sister study that seeks to validate results from two identical protocols (being funded by NAMM and others), we can't make any real decisions on what is happening.
Would I like this to show that for every instrument but flute you're golden? Yes! I know another study is looking at the WinDefenders impact now on them (I'm hopeful).
The real problems with wind instruments may not even be the expelling of air, but how spit is handled from the instruments. I believe the CSU study is also looking at that aspect. How much of a virus particle comes out from there? Even if COVID-19 wasn't the issue, I think all of these studies are good for our profession to put to rest one way or another safety we should be thinking about. If a great deal of virus particles do come out of the spit, a kid steps in it, and then touches their shoe in the locker room - then who knows what else?
Schools will start up in some capacity this fall - what ends up happening for us in Texas probably has less to do with science, and more with Friday nights. If football is to happen they're going to have to overlook a great deal of risk and put kids back full time. The real concern for all of us should be the support staff, custodians, maintenance, bus drivers, older substitutes, and such... I worry about many of them becoming casualties in a rush back.