This past Sunday the Los Angeles Times did something that no other newspaper has ever done. It published an analysis of the performance of 6,000 Los Angeles Unified School District teachers based on test scores.

To accomplish this, three Times reporters worked with a RAND Corporation researcher to implement a statistical approach known as value-added analysis, which rates teachers based on their students’ progress on standardized tests from year to year. Each student’s performance is compared with his or her own in past years, a process that partially controls for outside influences (like poverty) that can affect student achievement.

The paper published profiles of high- and low-performing teachers, along with some analysis. Here’s an excerpt summarizing some of its findings:

• Highly effective teachers routinely propel students from below grade level to advanced in a single year. T