Students are in class to be taught. People may point to some students who never do anything, but an average result would correlate to the quality of the teacher. Having gone through much of the educational system, I completely believe that a teacher can make all the difference in a student. These tests should be graded on a students CHANGE in the past year, instead of taking the test based off his baseline intelligence.
The teacher is responsible for ensuring that his or her students understand the material being taught. Poor achievement tests could be a sign that a teacher's method of teaching is not very effective. Therefore, a teacher may need more additional training. Also, judging a teacher based on student achievement tests can help to alleviate any biases or prejudices that a teacher may have. If a teacher knows that everyone must pass, he or she is more likely to try to help all students.
There is no possible way to gauge a teacher's performance based on their students' performance. There is always going to be a student that just doesn't care about school, this person will not try regardless of the teacher's efforts. There will also be student who simply won't be able to understand the material. Try as they might, the teacher might just not be able to make the information understandable for some students. Teacher's performance should be based on lesson plans as well as their efforts on helping their students.
Student achievement tests should not be used to judge teachers performance. It has been proven time and time again that tests do not adequately measure student performances. Teachers can not help if heir students are unwilling to learn or try. This is why inner city schools perform worse on tests. Teachers can not be judged on student performance.
I think it would be unfair and inaccurate to judge a teacher based on the achievement test by their students. While I do think that some teachers are not doing a good job, there are better ways to judge them. Using tests to evaluate the teachers themselves in one such strategy.