It really doesn't, as long as the teachers are the responsible adults in the room and engage in the science of isolating, distancing, masking and the other measures which front line medical workers practice every day.Which ignores teachers potential exposure to other adults.
My niece is a music teacher and choir director in a school system that has been fully open and operating since last August. You can literally count on one hand how many teachers have tested positive for covid. They all engage in the proper measures to keep everybody safe.
One of my best friends is a professor at the University, where it gets trickier because you're dealing with mostly adults and not little kids. All of his classes all year long have been in-person, with ridiculously low infection rates. To date, he's the only person in his department, students included, that has tested positive. His only symptoms were he could only taste salty and sweet but no flavors, and he had a slight fever for one day which prompted him getting tested. He isolated at home for 10 days (coincidentally over Christmas break) and went back to work, so he didn't miss any classes.