Peter Greene just keeps writing hit after hit. This
one explains what VAM means and why it works well in
manufacturing but not in dealing with human beings.

He explains how
Pennsylvania measures teacher quality: PVAAS uses a
thousand points of data to project the test results for students.
This is a highly complex model that three well-paid consultants
could not clearly explain to seven college-educated adults, but
there were lots of bars and graphs, so you know it’s really good. I
searched for a comparison and first tried “sophisticated guess;”
the consultant quickly corrected me—“sophisticated prediction.” I
tried again—was it like a weather report, developed by comparing
thousands of instances of similar conditions to predict the
probability of what will happen next? Yes, I was told. That was
exactly right. This makes me feel much better about PVAAS, because
weather reports are the height of perfect prediction.
Here’s how it’s supposed to work.

The magic formula will
factor in everything from your socio-economics through the trends
over the past X years in your classroom, throw in your pre-testy
thing if you like, and will spit out a prediction of how
Johnny would have done on the test in some neutral universe where
nothing special happened to Johnny. Your job as a teacher is to get
your really Johnny to do better on The Test than Alternate Universe
Johnny would. The only thing that goes wrong is that it
doesn’t work. Students are not inanimate objects like pieces of
steel. So he concludes: This is one more example of a
feature of reformy stuff that is so top-to-bottom stupid that it’s
hard to understand.

But whether you skim the surface, look at the
philosophical basis, or dive into the math, VAM does not hold up.
You may be among the people who feel like you don’t quite get it,
but let me reassure you– when I titled this “VAM for Dummies,” I
wasn’t talking about you. VAM is always and only for dummies; it’s
just that right now, the dummies are in charge.
See? All that’s required for VAM to work is believing
that the state can accurately predict exactly how well your
students would have done this year if you were an average teacher.
How could anything possibly go wrong??