The Value-Added Nightmare for Teachers
Since it was first introduced, the value-added model has been controversial. But the real damage is only now becoming apparent as school districts make it an important part of teacher evaluations.
Seven teachers in the Houston Independent School District and their union are suing the district to put an end to the use of the model, arguing it is unfair and violates their due-process rights ("Seven teachers and their union are suing HISD to end evaluations tied students' test scores," Houston Chronicle, May 1). I expect the decision to be appealed, eventually affecting evaluations in other districts across the nation.
You don't have to be an expert to realize that something is terribly wrong when teachers who rank highly one year fall to the bottom the next. But that is precisely what has happened in Houston, which implemented the model in 2007. The Economic Policy Institute warned that the value-added model was fundamentally flawed: "VAM estimates of teacher effectiveness should not be used to make operational decisions because such estimates are far too unstable to be considered fair or reliable"("Problems With the Use of Student Test Scores to Evaluate Teachers," Aug. 29, 2010).
Defenders of the model argue that these aberrations disappear when data are collected over enough time. But a report from the Department of Education released in July 2010 showed that even with three years of data, one in four teachers was likely to be misclassified because extraneous variables contaminated the results.
Making matters worse, teachers cannot challenge the results of their ratings, which is a violation of their right to due process. The irony is that the model is so complex even psychometricians don't fully understand it. If so, how can teachers be expected to? Yet their jobs depend on test scores.
Despite the inherent problems, I don't think the model will disappear. Reformers are determined to abolish tenure. Using the value-added model is one way of achieving that goal. Teachers in New Jersey, for example, will lose their tenure if they receive below-satisfactory ratings for two consecutive years. That opens the door to abuses. Principals can assign the hardest-to-teach students to teachers they don't like for one reason or another for two years running, and then use the data to fire them.