A Chicago Teacher: Why I Am Striking « Diane Ravitch's blog:
"The school board also wants to institute “merit” pay and use “merit” in our evaluations based on test scores. But how do you really measure “merit”? Do rising student test scores measure “merit”? Does this even work for the music teacher of the foreign language teachers whose subject does not even appear on standardized tests? Perhaps. But teachers receive different students every year. How do you account for differences in the students taught from year to year? How do account for students’ home life? The district has some complicated statistical model which supposedly measures the “value added” by a teacher.
But is this valid? In New York, they are trying to do this. But under this model, there have been teachers receiving wildly different numbers in the same year and wildly different numbers from year to year. If the masters of the universe cannot even properly mathematically model the value of a credit default swap on Wall Street, how can they measure the infinitely more complicated contribution that a teacher makes for her/his students in a year? This is not “merit” pay. This is random pay."