Teaching is a value-added activity
Standardize tests suck at measuring the value of a teacher. "Test scores largely reflect whom a teacher teaches, not how well they teach," notes Stanford Professor Education, Linda Darling-Hammond. "In particular, teachers show lower gains when they have large numbers of new English-learners and students with disabilities than when they teach other students."
The LA Times: "Research has repeatedly found that teachers are the single most important school-related factor in a child's education."
False. Parenting, motivation, and IQ are at least as important, if not vastly more important, to the success of a student than a teacher. Teachers can bring out the best in a student, but a child from a broken home and with an abuse parent just isn't going to do as well.
See also: The ballad of Pascale Mauclair, New York City's worst public school teacher.
One way of evaluating teachers, currently the subject of intense interest and research, are value-added approaches, which typically compare a student's scores going into a grade with his or her scores coming out of it, in order to assess how much "value" a year with a particular teacher added to the student's educational experience. The report expresses concern that the department's proposed regulations place excessive emphasis on value-added approaches. Too little research has been done on these methods' validity to base high-stakes decisions about teachers on them. A student's scores may be affected by many factors other than a teacher -- his or her motivation, for example, or the amount of parental support -- and value-added techniques have not yet found a good way to account for these other elements.
The report also cautions against using the National Assessment of Educational Progress, a federal assessment that helps measure overall U.S. progress in education, to evaluate programs funded by the Race to the Top initiative. NAEP surveys the knowledge of students across the nation in three grades with respect to a broad range of content and skills and is not aligned with the curriculum of any particular state. Although effective at monitoring broad trends, it is not designed to detect the specific effects of targeted interventions like those to be funded by Race to the Top.
More: NAP.