Given the challenges facing American public education today, identifying effective teachers is a more vital task than ever before. A wide body of student achievement research shows that teachers are the most important school-based factor — that is, not having to do with the student’s innate cognitive abilities or family background. Unfortunately, the current system does a poor job at identifying the effective and ineffective teachers. That system needs to be changed.

In the U.S. public school system today, the method used to determine teacher effectiveness — and thus to drive salary, promotion and tenure decisions — is based on a few external credentials.