In many places you can't get rid of the bad teachers - largely because of overly powerful unions. People who would make good teachers are driven away from teac

In many places you can't get rid of the bad teachers - largely because of overly powerful unions. People who would make good teachers are driven away from teaching by the perverse incentives. Yes, the number of good teachers is finite, but so few of them are actually in front of students that the upper limit hardly matters for the foreseeable future.