Unfortunately, I don’t think there has been research here.

Hopefully since the start of COVID (it is not over) any new builds or upgrades will include fresh air and filters. This is already done for large gatherings of national leaders so the tech is available.

Perhaps dust and particulates? The SoCal area is very dusty. If you leave your car parked for a few days it will have a fine layer of dust on it.

Imagine breathing that in along with all the other germs normally present in a classroom. Less sickness should allow more learning.

Related - https://www.vox.com/2020/1/8/21051869/indoor-air-pollution-student-achievement

There was a leak at a methane storage facility in the LA area. Several schools were provided air filters well after the event (methane is lighter than air). They had the filters for four months even though the methane levels were normal. Test scores increased.

I can’t fix this from my phone. Need to get to my desktop.

I’ll ban them from my community

CL is huge in larger metro areas like LA or SF Bay area. I’ve bought and sold many vehicles plus smaller stuff.