Nothing is every as simple as it seems. Except Algebra. Algebra's easy. I could show you, but you'd need a vacancy first . . .

Filling vacancies is not a straightforward issue. It's obviously not just a matter of openings vs. teachers: they have to be the right teachers. That is, at the very least, in the correct subject area and with the background necessary for whatever the student population happens to be. And then, of course, are the internal politics that keep veterans out of a school because they just cost too darn much. (It wasn't that long ago in NYC that teachers were "revenue neutral" for the school's budget. Then the principals were forced to do what the mayor couldn't. But enough politics, Have a Nice Day!)