The controversy over the use of standardized tests for evaluation purposes is the result of the assumption that those tests currently in widespread use are capable of differentiating between effective and ineffective teachers.
Contrary to popular belief, there is no evidence to support the belief that valid inferences can be made in this regard. That's why educators are so strongly opposed, not because they want to avoid accountability.
A fairer way of evaluating teachers is the collective judgment of experienced colleagues who have been trained and certified for this purpose. But testing companies will resist to the bitter end in order to protect the enormous profits they make under the present system.