The foundation and others have estimated that it could cost between 1.5% and 2% of the overall budget for teacher compensation and benefits to implement a feedback and evaluation system based on multiple measures of teaching performance.

CNN: Bill Gates: Invest in better teaching

Starting in 2009, the Gates Foundation supported a project known as the Measure of Effective Teaching, or MET, which worked with 3, 000 teachers to come up an evaluation and feedback system that helped teachers improve.

FORBES: Bill Gates Says There Is Something Perverse In College Ratings