My wife is in a similar situation. She's a middle-school teacher at a public school in a state that doesn't value public education. While she still loves teaching, her experience mirrors your's in regards to overwork, attrition, etc. For a job that should get off at 3pm, she routinely works all evening on grading, lesson planning and other admin tasks.

We also live in an area where teachers are poorly compensated relative to the cost of living. I'm well paid as a software engineer, which just makes her feel worse about the value of her career in teaching when she works longer hours than I do.

We've talked about her leaving teaching at the end of the school year with the plan to get her PhD so she can teach at a college level.