It’s hard to imagine any long-term improvement in the public schools that does not involve some combination of encouraging good teachers to teach and encouraging bad teachers to do something else. This is all the more important in light of the difficulty of predicting someone’s teaching ability before he or she is hired.
Fortunately, once we get a look at them in the classroom and we can distinguish the good from the bad, there is no mystery about how to retain the former and eliminate the latter. If we pay good teachers more, we’ll attract and retain at least some good teachers who would otherwise do something else. If we pay bad teachers less (all the way down to zero in the cases of teachers who should be fired), we’ll induce them to pursue other opportunities.