There are something like 3.5 or 4 million teachers in the US, so for sure they are not all self-sacrificing saints and there will be a broad mix of motivations.

There are something like 3.5 or 4 million teachers in the US, so for sure they are not all self-sacrificing saints and there will be a broad mix of motivations. But FWIW my experience is not like yours. I am a college professor and have seen many students over the years go into teaching, either at the secondary or elementary level (specifically, math teaching). When I meet with them to discuss what they want to do, almost all express that when they think about careers, their interest in teaching is because it is a reasonable career with reasonable pay, yes, but just as important to them is the sense of doing good, of directly helping people. (I have less experience with people in the services but what experience I do have is in the same direction.)