You don't know many teachers. The system consumes a little bit of teacher's altruism as a raw material, converting it to extra money for those other things mentioned. Too much and turnover becomes too high so they seem to carefully feel out to edge. You can shear sheep over and over but skin them only once.

Every public school teacher I've ever known (including the several in my family), from rich districts to poor, end up buying basic supplys for their students because they can't get the district to provide them. Its all very 20th century soviet. I've know teachers who waited six months for light bulbs before finally going to Home Depot and buying them themselves.