Besides a percentage of injected kids, and besides their being around shedding adults, we've been around parents whose school-attending kids are having high amounts of respiratory and sinus infections.
After some poking around, we found that one school had suffered a pipe burst during plandemic shutdown, and lots of kids and staff have been having issues. I believe they will find mold eventually. I also believe from another parents' talk with operations personnel that the HVAC units have not been cared for, run, ducts cleaned out or had timely filter changes.
(Just another reason to homeschool) But- if your kids or others are getting sick, push for answers and do what you have to so they're safe.
Except that I'm seeing kids who have not been wearing masks and who are not injected come down with respiratory issues that docs are trying to blame on allergies, which they don't have. Their classmates and the teachers are getting the same symptoms, and complain of musty odors, at least in one school. Don't fall for the one-solution-to-everything fallacy.