Value-Added In Teacher Evaluations: Built To Fail
With all the controversy and acrimonious debate surrounding the use of value-added models in teacher evaluation, few seem to be paying much attention to the implementation details in those states and districts that are already moving ahead. This is unfortunate, because most new evaluation systems that use value-added estimates are literally being designed to fail.
Much of the criticism of value-added (VA) focuses on systematic bias, such as that stemming from non-random classroom assignment (also here). But the truth is that most of the imprecision of value-added estimates stems from random error. Months ago, I lamented the fact that most states and districts incorporating value-added estimates into their teacher evaluations were not making any effort to account for this error. Everyone knows that there is a great deal of imprecision in value-added ratings, but few policymakers seem to realize that there are relatively easy ways to mitigate the problem.
This is the height of foolishness. Policy is details. The manner in which one uses value-added estimates is just
