From Diane Ravitch’s Bridging Differences blog on Education Week — the best explanation I’ve read yet for why it’s not valid to use student test scores in teacher evaluation:
I received an email from Dr. Harry Frank, an emeritus professor of psychology at the University of Michigan who has written textbooks about testing and measurement. Dr. Frank wrote that the first principle for valid assessment is that “no assessment can be used at the same time for both counseling and for administrative decisions (retention, increment, tenure, promotion). … All this does is promote cheating and teaching to the exam. … This principle is so basic that it’s often covered in the very first chapter of introductory texts on workplace performance evaluation.” [The full text of Dr. Frank’s email is posted on my Web site, www.dianeravitch.com, in a section called “comments.”] I asked Dr. Frank to explain the word “counseling,” and he said that this meant “feedback on performance for purposes of skills development,” what we might think of as the diagnostic use of an assessment. Dr. Frank also added: “Assessments should be a counseling resource, not a source of extrinsic motivation, i.e., rewards and punishments for teachers, administrators, and school districts.”
Put simply, tests and assessments should inform teachers about student progress and their own teaching, i.e., what can be learned from the test results. But it is inappropriate to use the same test results to hand out bonuses and punishments, promotions and tenure.