Why it’s no surprise high- and low-rated teachers are all around

This from GothamSchools:

The New York Times’ first big story on the Teacher Data Reports released last week contained what sounded like great news: After years of studies suggesting that the strongest teachers were clustered at the most affluent schools, top-rated teachers now seemed as likely to work on the Upper East Side as in the South Bronx.

Teachers with high scores on the city’s rating system could be found “in the poorest corners of the Bronx, like Tremont and Soundview, and in middle-class neighborhoods,” “in wealthy swaths of Manhattan, but also in immigrant enclaves,” and “in similar proportions in successful and struggling schools,” the Times reported.

Education analyst Michael Petrilli called the findings “jaw-dropping news” that “upends everything we thought we knew about teacher quality.”

Except it’s not really news at all. Value-added measurements like the ones used to generate the city’s Teacher Data Reports are designed precisely to control for differences in neighborhood, student makeup, and students’ past performance.

The adjustments mean that teachers are effectively ranked relative to other teachers of similar students. Teachers who teach similar students, then, are guaranteed to have a full range of scores, from high to low. And, unsurprisingly, teachers in the same school or neighborhood often teach similar students.

“I chuckled when I saw the first [Times story], since the headline pretty much has to be true: Effective and ineffective teachers will be found in all types of schools, given the way these measures are constructed,” said Sean Corcoran, a New York University economist who has studied the city’s Teacher Data Reports....