Why Tests Scores CAN'T Evaluate Teachers
I'm going to have more to say about Jonah Rockoff's testimony before the New Jersey State Board of Education last week. See here and here for previous posts; Bruce Baker also opines in a must-read post.
But right now, I want to use a specific part Dr. Rockoff's presentation to address a very serious problem with the entire notion of test-based teacher accountability. Keep in mind that Rockoff talks about Student Growth Percentiles (SGPs), but the problem extends to just about any use of Value-Added Modeling (VAM) in teacher evaluation based on test scores. Go to 1:07 in the clip:
But right now, I want to use a specific part Dr. Rockoff's presentation to address a very serious problem with the entire notion of test-based teacher accountability. Keep in mind that Rockoff talks about Student Growth Percentiles (SGPs), but the problem extends to just about any use of Value-Added Modeling (VAM) in teacher evaluation based on test scores. Go to 1:07 in the clip:
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The key element here that distinguishes Student Growth Percentiles from some of the other things that people have used in research is the use of percentiles. It's there in the title, so you'd expect it to have something to do with percentiles. What does that mean? It means that these measures