About 'Grading the Teachers'

Under value-added, a student's progress  is measured against what would be expected based on scores from previous years. The difference is the value that a teacher added — or subtracted. Because the method compares each student to his or her own past performance, it largely controls for social and economic disparities among students. More detail on the approach can be found at http://www.latimes.com/teachers.

This analysis follows one The Times published in August rating 6,000 elementary teachers and their schools through the 2008-09 school year. In the coming weeks, The Times will publish an updated database including the rankings of individual middle school teachers and an additional year of data for both middle and elementary school teachers. Data are not available for teachers of subjects other than math or English.