Resident Scholar Frederick M. Hess

At the 2008 Democratic convention, Barack Obama promised to "recruit an army of new teachers and pay them higher salaries and give them more support, and in exchange I'll ask for higher standards and more accountability." Like most of what Obama says, this sounds wonderful. The trick, though, is that if you consider only objective factors, it's very hard to tell good teachers from bad ones.

All the observable characteristics that researchers can measure, including everything from licensure status to verbal acuity, explain less than 10 percent of the variation in student performance across classrooms. While the nation's 3.3 million teachers matter a lot, credentials and seniority have very little to do with how well they educate our children. Yet credentials and seniority are what determine most teachers' pay.

Leaving such formulas aside, competent school and district leaders have a pretty good idea of which teachers are doing good work. Like anyone who runs an organization where paper metrics are poor predictors of quality, they should be able to compete aggressively for the widest possible pool of talent, monitor performance, weed out mediocrity, and reward excellence. The reason they usually can't do this is that our schools still rely on the industrial model that prevailed for most of the 20th century.

How can schools address this situation? Overhaul state licensure systems, which deter applicants who have not been credentialed by schools of education, to make them receptive to talent--including Teach for America recruits and career switchers. Emulate education officials Joel Klein of New York City and Michelle Rhee of Washington, D.C., by devising smart ways to evaluate performance and then pushing to remove ineffective teachers. Put new dollars into rewarding excellence, scarce skills, and challenging assignments instead of making new hires. And, since having teachers do the same job for decades is a sure way to repel talent, rethink the profession to include more options for change and growth.

Frederick M. Hess is the director of education policy studies at AEI.