Evaluating Teachers Via "Value Added"

I was a fan of "value added measure" back in the late 1990s, then the evidence seemed to turn away from its validity.  A little more esoteric use of statistics and VAM is back in the game:

Is evaluating teachers an exact science? Many people — including many teachers and their unions — believe current methods are often too subjective and open to abuse and misinterpretation. But new tools for measuring teacher effectiveness have become more sophisticated in recent years, and several large-scale studies in New York, Los Angeles and North Carolina have given those tools more credibility. A new study released on Monday furthers their legitimacy; and as the science of grading teachers advances, it could push for further adoption of these tools...

 But the economists on both sides of the Vergara case are still engaged in cordial debate. On one side is Raj Chetty of Harvard University, John Friedman of Brown University and Jonah Rockoff of Columbia University — hereafter referred to as “CFR” — who authored two influential papers published last year in the American Economic Review; Chetty testified for the plaintiffs in the case. On the other side is Jesse Rothstein, of the University of California at Berkeley, who published a critique of CFR’s methods and supported the state in the Vergara case.

On Monday, to come full circle, the CFR researchers published a reply to Rothstein’s criticisms.

At the center of this debate are evaluation models that try to isolate the educational value added by individual teachers, as measured by their students’ standardized-test scores relative to what one would expect given those students’ prior scores. The hard part, as Friedman says, is to “make sure that when you rate a teacher, that you actually rate what the teacher has done, and not whether they had a bunch of very poor or very rich students.”

I draw your attention to the source of the excerpt above.  Very interesting.