Teacher Evaluations: An Interesting Take On Value Add

Recently New York city published the results of a three year study on teacher’s scores.  The scores are based on the value-add mentality.  This is the idea that a teacher can influence a student in their class and the measurement of this value is tracked by how well a student does on tests in the years following having had that teacher in class.  From the perspective of someone who works in an industry that tries very very hard to measure the intangibles, I think this is a very clever method of determining impact.

Predictably the teachers and the teacher unions are objecting.  And the range of reasons is fascinating.

First, how does this whole thing work:

 The ratings, known as teacher data reports, covered three school years ending in 2010, and are intended to show how much value individual teachers add by measuring how much their students’ test scores exceeded or fell short of expectations based on demographics and prior performance.

Pretty solid reasoning.  We’re pretty good at using inputs to determine future performance.  Pretty good as long as we’re using a large enough sample.  So the idea that a fantastic teacher increases her students scores should not strike us as alien.  Rather it should seem reasonable.

And to be sure, there are some shortcomings with the system that need to be addressed:

Such “value-added assessments” are increasingly being used in teacher-evaluation systems, but they are an imprecise science. For example, the margin of error is so wide that the average confidence interval around each rating spanned 35 percentiles in math and 53 in English, the city said. Some teachers were judged on as few as 10 students.

As I mentioned, there is work to do.  But the attacks on the system are incredible:

I believe the teachers will be right in feeling assaulted and compromised here,” Merryl H. Tisch, the chancellor of the State Board of Regents, said in an interview. “And I just think, from every perspective, it sets the wrong tone moving forward.

As if.

This is a group of professionals whose LIVING it is to adjudicate grades of students who are submitting subjective works.  How can a teacher who claims to be able to decide the grade of an essay on the merits of the Shylock’s lending practices from the “Merchant of Venice” compared to modern day lending practices be able to look me straight in the face and say that I can’t also adjudicate HER grade?

Or a sociology teacher grading a report on the impact of gay marriage on traditional married households.  If you can grade THAT how can you argue that I can’t grade YOU?

You can’t.  Plain and simple.  Teachers are afraid of being exposed held accountable.  And THAT is tragic.  We trust these people to educate and hold responsible our kids for God’s sake.  The fact that they feel that they themselves are above such accountability is criminal.

With all that said, the best, absolute best, argument against value-added grading was this:

What many teachers point out is that the scores cannot account for many other factors: distractions on test day; supportive parents or tutors; allergies; a dog continually barking near the test site.


So, while teachers are going to pooh pooh the very same arguments their student give THEM they are only to willing to make the case that “My dog ate the homework.”


We need strong teachers.  Identify the very best and shower them with riches.  And the very worst?  Fire them as quickly and as soon as possible.

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