It will not give teachers an incentive to improve their teaching. Teaching is a calling, not something you choose for the money. Teachers are what we call 'intrinsically motivated': they want to realize an ideal, in this case, educating and raising responsible citizens. Recasting this ideal into a financial reward system actually demotivates teachers who feel the inherent value of their work now suddenly has become sullied by chiefly monetary rewards, which is why performances pay hasn’t worked in many places. [1]  [1] White, Performance pay for teachers is a terrible idea and here’s why, 2011