Perdido 03

Perdido 03

Wednesday, February 29, 2012

The Unbearable Randomness Of VAM

GF Brandenburg does a great job of succinctly summing up Gary Rubenstein's two part analysis of the value-added measurements that were used in the Teacher Data Reports:

He discovered several very important things:

(1) There is almost no correlation between a teacher’s score in 2009 to that for the following year.

(2) There is almost no correlation between a teacher’s score when teaching math and when teaching reading – to the same kids, the same year, and in the same elementary class.

(3) There is almost no correlation between a teacher’s score when teaching different grade levels of the same subject (i.e., Math 6 versus Math 7, and so on).

In other words, the Value Added Methodology is very close to being a true random number generator — which would be great if we were playing some sort of fantasy role-playing game or a board game like Monopoly or Yahtzee. But it’s an utterly ridiculous way to run a school system and to evaluate teachers.

I highly recommend reading his two blogs on this topic, which are here (for the first part) and here (for the second part).

After you read them, you need to pass the word (email, word of mouth, twitter, Like, facebook, whatever).

We need to kill this value-added mysticism and drive a special wooden stake through its evil, twisted heart.

The NY Times reports that the VAM rankings released for charter school teachers yesterday had an even higher margin of error than the ones released for traditional public school teachers last Friday.

Nothing like using an evaluation system with a maximum margin of error of 75% in math and a maximum margin of error of 87% in English to publicly humiliate teachers.

Of course the Mayor of Money says he has no problem with this - no evaluation system is perfect, but we need to evaluate teachers, this is the best we can do, and the data must be made public.

Would Bloomberg trust a political poll with a MOE of 87%?

Would Bloomberg trust a company that had a 75% MOE on its reported earnings?

Nope - but he trusts an eval system with that kind of MOE.

It's time to send the Little Autocrat back to Bermuda and take away his control of the NYC school system.

Seriously - he's not trying to improve public schools.

He's trying to destroy them - and teachers too.


  1. Indeed! Nice post heading too!

  2. Said it before and will say it again.... you are the best-great post!!!