Anthony Cody calls out John Merrow for inconsistency on the Vergara decision. Merrow, Cody notes, has become increasingly outspoken as a critic of high-stakes testing, et fails to appreciate that his support for the Vergara decision is support for bubble testing as the ultimate judge of teacher quality.

Cody writes:

“The Vergara decision follows the poorly founded logic of the Chetty study, which makes dubious claims of future student success based on differences in test score gains between teachers. What is the effect on teachers and students when “student performance” becomes a factor in teacher evaluation – as Merrow advocates here? Student performance is almost always measured by test scores, and we already have many states that have gone down this path, and are using Value Added Models to predict what student test scores should be, resulting in poor evaluations for teachers whose students don’t grow as fast as the VAM system predicts they should. English learners, special ed, and even the gifted and talented tend to perform poorly in these systems, meaning that teachers who work with these students are likely to suffer from poor evaluations. And ALL teachers will be obligated to make whatever tests are used for these purposes central to their teaching, to avoid being terminated.

“Merrow closes his post with this statement:

“The effort to blame poor education results on teachers and unions is misguided and malicious. It’s scapegoating, pure and simple, but-it must be said-protectionist policies like those in California play into the stereotype.

“Let’s think about what this stance suggests we ought to do.

“In spite of the fact that the effort to blame poor results on teachers and unions is totally wrong, we should capitulate to the central demands of the “reformers.” Get rid of seniority. Base evaluations – and the decision as to who is terminated — more on student performance (test scores) and principal judgment.

“The result will be to make a profession that has become less and less desirable, even less so.

“Turnover has already been on the rise. Charter schools already are demonstrating the model at work, and have significantly higher teacher turnover to show for it. Moving public schools in this direction will drive turnover upwards there as well. Turnover has been shown to have a strong negative effect on student performance. This report should not be forgotten. It found that:

“For each analysis, students taught by teachers in the same grade-level team in the same school did worse in years where turnover rates were higher, compared with years in which there was less teacher turnover. 


“An increase in teacher turnover by 1 standard deviation corresponded with a decrease in math achievement of 2 percent of a standard deviation; students in grade levels with 100 percent turnover were especially affected, with lower test scores by anywhere from 6 percent to 10 percent of a standard deviation based on the content area.


“The effects were seen in both large and small schools, new and old ones. 


“The negative effect of turnover on student achievement was larger in schools with more low-achieving and black students.”

Cody maintains that low-performing schools need a policy of teacher retention, not teacher firing.