1) People get bloody well shot in retail stores for trying to insist on masks. Is Mrs. Crabapple supposed to face down some covid-denier with an assault rifle for making little Johnny cover his mouth and nose?
If a mask could stop 2 people from getting infected (I'm not going by statistics here, just an example number), who could then infect more people, who would then infect more, until eventually people will die from your infecting these 2 people, someone being shot seems like a lower risk for death than coronavirus infection. It is horrifying that we have to compare these risks here in America. I've only seen a few examples of people being shot over mask-related problems.
Also, Covid-19 is contagious. Rage-induced shooting rampages don't seem to be.
2) Masks are excellent... for short, casual contact. Wear one in the grocery, or on the street, and you are unlikely to infect a passerby. This breaks down when you have people in an enclosed space, sharing air. Kids are in classrooms breathing each other's air for hours and hours - the mask isn't really going to save them.
Yeah, masks aren't great in those circumstances. This more illustrates the point that going back to school is a bad idea no matter what the safety measures are more than anything else. It reduces spread, and if the desks are far enough apart, it is more unlikely to spread the virus. I don't know if many (if any) schools will have those precautions.
Also, maybe if more people wear masks, more will jump on the bandwagon (hasn't seemed to work yet, but who know? Maybe if their kids have to wear masks, some people will start wearing masks?)
3) Given 2, not enforcing masks gets them to have an outbreak quickly and the school shut back down, which might actually minimize the impact.
Or it could lead to just a spread in Coronavirus if they don't close the school down. I don't think the people who are pushing for re-opening schools mid-pandemic will want to stop re-opening just because of an increase in cases. The current increase in cases hasn't done much to stop the opening up.