I want to explain something in the most easy way I possibly can. I want to explain it so anyone can understand it. It is important that everyone who has anything to do with education in New York State understands it.

On Wednesday September 16, 2015 the New York State Board of Regents, under the leadership of board chancellor Merryl Tisch created a process whereby teachers can appeal their effectiveness ratings. The formula for the ratings recently changed, with test scores moving from making up 20% of a teacher’s rating to student test scores now making up to 50% of a teacher’s rating.

New York State has been using a “student growth” formula for their calculations of how much “value” an individual teacher has added to the “achievement” of a class of students. Because I am trying to keep this post as simple as possible I will not go into a long explanation of the problems with Value Added Measures in general, or the Growth Percentile Scores in particular. (Read the linked articles for explanations of what the mathematical models can measure and what they cannot measure.)

What is extremely important for all New York State educators and families to understand is that the Chancellor of the Board of Regents does not understand a very basic aspect of a policy she has foisted upon us. Quoting from Geoff Decker’s piece on Chalkbeat:

“In the interview, Tisch said she sympathized with Long Island teacher Sheri Lederman, who is suing the State Education Department over her 2014 evaluation. Lederman’s students scored well on state tests and her superintendent gave her glowing reviews, earning her an ‘effective’ overall rating. But the “’ineffective’ rating she received on the portion based on her students’ test scores prompted her to file a lawsuit, which is now making its way through the State Supreme Court.

‘It disturbs me greatly,’ Tisch said of Lederman’s case. ‘One of the reasons we’re putting in place this appeals process is to deal with those kinds of aberrations.'”

“Those kinds of aberrations”. Let that sink in. Chancellor Tisch, in charge of guiding educational policy for the entire state of New York, understands the fluctuation of Value Added and Student Growth Scores as “aberrations” rather than as a function of how the formulas actually work. Sheri Lederman’s lawsuit in New York State does not rely on an argument that her rating was based on a mistake or aberration.

Tisch’s misconception that Lederman’s growth score ratings are an “aberration” could be easily corrected if she read the New York State Department of Education’s Court filings and oral argument in the Lederman case. Indeed, it is the official position of New York State that Lederman’s rating was not an aberration, but actually a consequence of how the model is supposed to work.

How can we help Chancellor Tisch (and the 10 Regents who voted with her and Governor Cuomo) understand the very basic idea here? Value Added Measures/Models or Growth Scores are not stable enough to rate individual teachers from year to yearPeriod. Full stop. There is nothing more to know here. Pass it on.