After a long legal battle, the New York City Education Department released individual performance rankings of 18,000 public school teachers on Friday, “while admonishing the news media not to use the scores to label or pillory teachers,” reports the New York Times.
The reports, which name teachers as well as their schools, rank teachers based on their students’ gains on the state’s math and English exams over five years and up until the 2009-10 school year.
Over the five years, 521 teachers were rated in the bottom 5 percent for two or more years, and 696 were repeatedly in the top 5 percent.
But citing both the wide margin of error — on average, a teacher’s math score could be 35 percentage points off, or 53 points on the English exam — as well as the limited sample size — some teachers are being judged on as few as 10 students — city education officials said their confidence in the data varied widely from case to case.
A teacher’s score can’t be considered in isolation, said the Education Department’s chief academic officer, Shael Polakow-Suransky. “No principal would ever make a decision on this score alone.”
If the margin of error really is that wide, I don’t see any value in the value-added scores.