Madison School Board Member Ed Hughes

Value added” or “VA” refers to the use of statistical techniques to measure teachers’ impacts on their students’ standardized test scores, controlling for such student characteristics as prior years’ scores, gender, ethnicity, disability, and low-income status.
Reports on a massive new study that seem to affirm the use of the technique have recently been splashed across the media and chewed over in the blogosphere. Further from the limelight, developments in Wisconsin seem to ensure that in the coming years value-added analyses will play an increasingly important role in teacher evaluations across the state. Assuming the analyses are performed and applied sensibly, this is a positive development for student learning.
The Chetty Study
Since the first article touting its findings was published on the front page of the January 6 New York Times, a new research study by three economists assessing the value-added contributions of elementary school teachers and their long-term impact on their students’ lives – referred to as the Chetty article after the lead author – has created as much of a stir as could ever be expected for a dense academic study.

Much more on value added assessment, here.
It is important to note that the Madison School District’s value added assessment initiative is based on the oft-criticized WKCE.