Ever since Americans sent their children to one-room schoolhouses, parents have known what makes a good school: inspiring, organized, and creative teachers. But researchers haven't been able to quantify what, exactly, makes a teacher effective and how to tie that to student achievement.

Now, the Bill & Melinda Gates Foundation--one of the most influential voices in education policy today--hopes to end that confusion. Nine years and $2 billion into its work to improve America's public schools, the Seattle-based foundation is turning its focus to teacher effectiveness.

"We've been sort of looking around for the silver bullet for education reform, and actually the answer has been right under our feet the whole time," said John Deasy, deputy director of the foundation's education work.

Over the next five years, the foundation plans to spend another half a billion dollars in its quest to figure out what qualities make the best teachers and how to measure those qualities in the classroom.

The project has two parts: research to develop and test methods to rate teachers, and experiments at a handful of school districts around the nation to try out new ways of recruiting, training, assigning, and assessing teachers.

Among those asked to submit proposals for a share of the money were school districts in Atlanta; Denver; Hillsborough County, Fla.; Memphis, Tenn.; Omaha, Neb.; Palm Beach County, Fla.; Pittsburgh; Prince George's County, Md.; Tulsa, Okla., and a group of Los Angeles charter schools.

This week, the foundation chose five finalists: Hillsborough County, Memphis, Omaha, Pittsburgh, and the Los Angeles charters. Final decisions will be made this fall.

The other five districts will be considered for smaller grants to pay for parts of their effective-teaching plans.

Their ideas, which were presented in Seattle earlier this month, focus on teacher training, putting the best teachers in the most challenging classrooms, giving the best teachers new roles as mentors and coaches while keeping them in front of children, making tenure a meaningful milestone, getting rid of ineffective teachers, and using money to motivate people and schools to move toward these goals.

"It really is about an effective teacher for every student, every year of their school career," said Vicki Phillips, director of the foundation's K-12 education program. "If we did that, we would make the kind of progress that we have all long dreamed about in this country."

Foundation officials said they were impressed with how thoughtful the districts were in their proposals and how clear it was that teacher's unions, school officials, and elected school board members worked together to come up with the ideas.

Pittsburgh Superintendent Mark Roosevelt said the process propelled his district forward. "I'd say we made almost 10 years of progress with our union in three months," he said. "It was like a door had been opened that we didn't know was in the wall any more."