Value-Added Models' Fatal Flaw
Much has been written about the corporate education reformers pet teacher evaluation tool the value-added model (VAM). A VAM is a statistical measure that attempts to account for a teacher’s effectiveness through student performance on standardized tests. These measures have been nearly universally discredited by study after study, most recently by the American Statistical Association, the leading professional organization for statisticians in the country. For an outstanding review of all that is bad about VAMs, I would recommend Rethinking Value-Added Models in Education: Critical Perspectives on Tests and Assessment-Based Accountability, by Audrey Amrein-Beardsley.
While VAMs do not come close to meeting the sniff test for reliability and validity, they have been forced down states’ throats as an accountability measure through the Obama administration’s Race to the Top program. Each of the 46 states that signed on is supposed to come up with a teacher evaluation system using VAMs in order to get a waiver from the impossible to achieve goals of the No Child Left Behind Act.
Whether VAMs are statistically suspect or not, they are doomed to fail. They have a fatal flaw that will insure that failure. Here is why.
What is the purpose of a program of teacher evaluation? For more than 95% of teachers the chief purpose of an evaluation is formative. In other words the evaluation is designed to help that teacher get better at teaching. Any smart Russ on Reading: Value-Added Models' Fatal Flaw: