Problems with Value-Added Models (VAMs)

What are VAMs?

VAM stands for Value‐Added Models. These are a variety of statistical techniques that try to
estimate how much a school or a teacher is contributing to student learning.

Why is the value‐added model dangerous?

VAM analysis is based only on test scores, and a VAM analysis of an individual teacher’s performance, because of the small number of students' scores, produces a lot of errors. Even with three years of test data, the U.S. Department of Education estimates that VAM will be wrong 25% of the time. A teacher can be evaluated as “effective" one year and "ineffective" the next. VAMs are not reliable and therefore they are not a statistically valid measurement for judging teacher effectiveness.

What is wrong with the LA Times publishing teachers' names and their effectiveness evaluation?

The Times presents these scores and their meaning as if they were facts. They are not. The Times reporters took student scores, applied an arbitrary statistical analysis formula and then labeled the results, indicating the analysis proved the teacher evidenced a specific level of effectiveness as a teacher. They did that while also admitting the margin of error is so huge VAM cannot be used to make personnel decisions. In spite of this, the LA Times published teachers’ names and ranked them using a single, very unreliable measure.

Why did the LA Times invest in this study and publish this article?

The LA Times is a business and their main goal is to stir up controversy to generate attention, gain readers, and sell newspapers. By dragging the names of individual teachers through the mud, they have turned a dry policy discussion of an obscure statistical technique into a sensationalized story that has garnered attention (and scathing critiques) throughout the nation and around the world.