Always amazes me that people think they can make education better by just pronouncing that things will change. The latest notion is to evaluate teachers based on the test scores of the students. This approach ignores are the other major variables that go into achievement on the part of children. Sure teachers are important. Does anyone notice that kids from higher socio-economic areas do better on tests and in school. Does that mean they have better teachers? Possibly, but it also means they have parents who are involved in the child's education because the parents value education themselves. These kids have parents who spend time with children doing homework or who hire someone who will. These are parents who take children places and expose them to travel, theatre and good music. How can a teacher replace that?
Then there are the variables that are within the child him or herself. Children are human beings and carry some of the same traits as all human beings. Some are highly motivated to succeed, others not so much. Some children are just smarter than others! I know we are not supposed to notice that. We are supposed to think that all children can achieve at the same level at the same time. Anyone who believes this myth has clearly not spent much time with kids. Any parent with multiple children can tell you how different they are from one another.
Children's abilities vary just like adults. Some children are better in the STEM subjects of science, technology, engineering and math. Others are better in the arts of English, other languages or social studies. Naturally they will do better in their areas of preference. Then how are we going to measure teachers who teach subjects for which there are no standardized tests. There are objective observable behaviors that measure good teaching. But we are afraid of doing the hard work to use those.
The bigger issue is that teachers have become blue collar workers who are afraid of any assessment. They want to get a raise every year for living and staying around. Teachers are no longer poorly paid. Someone should notice that. Teachers need to be willing to act like professionals and to earn their salaries based on how well they do their jobs. I do not think test scores measure that.