Is DCPS's new IMPACT Evaluation System Rigged?

On November 1, Valarie Strauss invited Columbia Teachers College professor, Aaron Pallas to analyze just how the new IMPACT teacher evaluation system works and his simple description (here) is a shocker. It turns out that teachers are not being evaluated against a standard of good teaching, but rather against the student test score achievement of similarly situated teachers in DCPS. So half the teachers will always be rated ineffective, and half effective, no matter how good the quality of teaching really is.  The question is, would it be the best use of DC tax dollars to extend the test based IMPACT model, now used only in 3rd, 5th, and 8th grades, on lots of new standardized tests so that teachers can be evaluated in this way at all grade levels and subject disciplines? Read the Pallas analysis and you'll probably demand that IMPACT be drastically modified so that its about good teaching, not a zero-sum game based on which student scores are higher and which lower.

[...which reminds us of a joke about two teachers camping in the woods. When they were about to go to sleep for the night, the one teacher started putting on his sneakers. "Why are you doing that?" asked his friend. "Bears," said camping teacher #1. "You can't outrun a bear," said camping teacher #2. "I don't have to outrun the bear, said #1. I just have to outrun you."]