Tuesday, December 09, 2008

A Great Teacher is X Times Better than a Lousy One

One of the weird things about evaluating teacher quality through "value-added" testing data is that most people would say that the results actually underestimate the true difference in value of a great teacher over a lousy one. Think of a fantastic teach you or your child has had; now think of a bad one. Is the first only three times better than the second? I think not.

It is only when you artificially narrow the definition of good teaching that the impact of teacher quality seems so small.

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