My wife used to teach 2nd grade. Do you want books for 2nd graders to read while at school? Well, guess who pays for them? Any learning activities that go beyond the chalkboard and pieces of paper? Those came from our pocket.
And then 80% of the parents fall into one of two categories: either they do nothing to help their children, or they are infuriatingly picky and critical about everything the teacher does with their perfect angel babies.
My wife lived to teach and was very good, but the salary very literally didn't cover the cost of daycare for the children. (Probably better for her to be home anyway).
They deserve some credit for what they do. Very underappreciated.