"The very concept of value-added assessment reflects the mind-set of statisticians and economists who measure productivity gains. A farmer plants corn of a certain variety in a certain type of soil, treats it with certain conditions, and then measures the growth of the crop to determine the worthiness of the treatment. In the context of value-added assessment, the teacher is the treatment. If the teacher is effective, the corn grows to a certain height. If the teacher is not, the corn does not grow or grows very little.
But children are not corn. (Emphasis mine.) They are not seeds or plants with fixed characteristics. Children's lives are not static. They have crises and ups and downs in their home lives and in their personal lives. Maybe their parents got divorced. Maybe a parent lost her job. Maybe a student broke up with her boyfriend or totaled the family car. Maybe a family member died. Maybe they were evicted from their home. These changes affect motivation, attention, and school performance. Children are not crops. They are not empty vessels waiting to be filled by a teacher."
I could go on and on citing the rest of her chapter. She makes a perfect argument and makes it so clearly that many people, not just teachers, can understand. Children are not crops, and teachers are not farmers. We cannot be evaluated and paid based on how a student performs on a test. It goes against logic and common sense.
If you want are intrigued and want to read more, go get this book!