It’s by design. They’re deliberatetly underpaid, because a teacher who’s well paid enjoys their job and does it well, which would make our public more informed and learned than is appropriate in a democracy like ours. So, public education is underfunded, denied the resources on which the annual production of a healthy and critically adept student body depends. This is also why there is such a push for vouchers and charter schools, privatized education that prioritizes profit over teaching children anything worthwhile beyond devotion to the state and its exceptionalism.