Nobody can seriously believe that masks and 6 feet of distance inside closed spaces will prevent the spread of Covid. Especially this Delta variant.
If the teacher was infected and symptomatic, s/he should have known better. Everyone knows by now. Even if not confirmed by tests, if you are feeling sick and showing symptoms, isolate yourself. This is true for any infectious disease.
That is true. So why are schools requiring kids to wear masks? Why is Home Depot requiring customers to put on masks?
Flimsy cloth masks don't stop aerosol viruses. Everybody should know that. The CDC certainly does, since they tell people those masks are not effective protection against dangerous airborne viruses.