most important part to this whole issue...."..and, as mentioned already, kids are PHENOMENAL ASYMPTOMATIC "SPREADERS"" (emphasis mine)...
The real world examples of kids bringing COVID into their households are everywhere...so, when all of this was going on and no vaccines were available until DECEMBER, much less being utilized, it is totally understandable why teachers would not want to risk their lives if alternatives - however less effective - were available.
Once the conditions you grudgingly acknowledge were put in place (ventilation, etc) and vaccines readily available (thank you, JB), those justifiably concerned teachers were able to return to the work they love.