New York City’s Department of Education (meaning, Mayor Bloomberg) and the United Federation of Teachers are wrangling about the formula for rating and ranking teachers and how much of it should be determined by test scores. The mayor still wants to publish the names of teachers along with their ratings so that parents will know which teachers to avoid and which to seek out. Imagine the chaos in schools when everyone wants to be in Ms. Smith’s class and no one wants to be in the classrooms of Mr. Jones, Ms. Green, or Col. Mustard.

It is important to remember how untrustworthy these formulae are.

Here is a good reminder. Aaron Pallas describes the “worst” eighth grade math teacher in New York City.

And here is the story of the “worst teacher” in the city of New York.

The New York Post plastered her name and picture in its pages, but it turned out that she teaches new immigrant students who cycle in and out of her class. The value-added ratings for her were meaningless.