Nonsense=makes no sense.

Last year, when the Chetty-Friedman-Rockoff study of teacher effects was published on the front page of the Néw York Times, it created a sensation. It seemed to say that the “quality” of a single teacher would raise lifetime earnings, reduce teen pregnancy, and have other dramatic effects.

The story said: “Replacing a poor teacher with an average one would raise a single classroom’s lifetime earnings by about $266,000, the economists estimate. Multiply that by a career’s worth of classrooms.”

One of the authors of the study said that the lesson was “fire bad teachers sooner rather than later.” This was used to support the test-based evaluation systems pushed by Race to the Top that otherwise had no evidence behind them (and still don’t). It also supported economist Eric Hanushek’s view that the “bottom” 5-10% of teachers, judged by their students’ scores, should be fired every year.

Just a few weeks later, President Obama cited the CFR study in his State of the Union address. He said: ” We know a good teacher can increase the lifetime income of a classroom by over $250,000.”

But it is all a great exaggeration.

Bruce Baker of Rutgers demolished the study here. He pointed out many flaws, including the fact that most teachers are not rated.

But what about the claim of earning an extra $266,000 or $250,000 per year per class over a lifetime?

Baker writes:

“One of the big quotes in the New York Times article is that “Replacing a poor teacher with an average one would raise a single classroom’s lifetime earnings by about $266,000, the economists estimate.” This comes straight from the research paper. BUT… let’s break that down. It’s a whole classroom of kids. Let’s say… for rounding purposes, 26.6 kids if this is a large urban district like NYC. Let’s say we’re talking about earnings careers from age 25 to 65 or about 40 years. So, 266,000/26.6 = 10,000 lifetime additional earnings per individual. Hmmm… no longer catchy headline stuff. Now, per year? 10,000/40 = 250. Yep, about $250 per year (In constant, 2010 [I believe] dollars which does mean it’s a higher total over time, as the value of the dollar declines when adjusted for inflation). And that is about what the NYT Graph shows: http://www.nytimes.com/interactive/2012/01/06/us/benefits-of-good-teachers.html?ref=education”

What this boils down to is that a student can get a lifetime boost of $5 a week if we now spend billions of dollars on value-added rating systems. Maybe. Or maybe not. ”

One of the authors wrote Baker to say that their calculations show that the actual gain per student would be about $1,000 a year or $20 a week.

There have been other criticisms of the study, some noting that the study was based on teaching before NCLB, before high stakes testing. Others questioned whether a large scale study of this kind could connect specific teachers to specific children. And one reviewer insisted that the study contradicted itself and said nothing.