Actors do it. Professional athletes do it. Now Bill Gates wants the country to spend $5 billion for every teacher in every classroom in every district to be filmed in action so they can be evaluated and, maybe, improve.

Among all his foundation's educational initiatives for things like smaller schools and new technology, Gates has increasingly zeroed in on effective teaching as the key lever to improve education, as he discusses in an exclusive interview in Fast Companythis month.

But how do you know effective teaching when you see it? Judging teachers by their students' test scores is crude and incomplete. In a talk he gave for a TED / PBS special to be aired May 7, Gates discussed a pilot program, the Measures of Effective Teaching, with 3,000 teachers in seven districts. They reported three years of findings in January on a teaching evaluation system that combines test scores, student evaluations, and classroom assessments, where teachers are graded by impartial observers.

The idea of reevaluating how we test teachers is spreading, but remains controversial--even without the privacy issues involved in filming the classroom. "I know some teachers aren’t immediately comfortable with a camera in the classroom," Gates acknowledged, then said that could be overcome by allowing teachers to pick which lessons they want filmed--which would seem to undermine the validity of any findings.

States and districts have already spent millions of dollars overhauling teacher evaluation systems, only to have districts rating 97, 98, or 100% of teachers as "satisfactory" or better.

In his talk, Gates emphasized the idea of using this feedback system to help teachers do their job better. "We need a system that helps all our teachers be as good as the best," he said. "Our teachers deserve better feedback." He clearly wants to be seen as a friend, not an enemy, of teachers. However, the MET project, at least, has done nothing to demonstrate that these evaluations can actually help teachers improve--rather than just weed out the good from the bad.