We have already seen that such incentives produce the wrong effect. At the whole-school level, what we see from incentives like this is that the system gets gamed such that the standard is lowered so that pay milestones are achieved, as opposed to the actual results of educating the children.

Tests get dumbed down. Teaching to tests instead of to understanding occurs.

Pay teachers more, but put them in a system where the students matter, not the money.