Based on the belief that the information is public — the data was released in response to a Freedom of Information request by news organizations — DNAinfo has created an interactive tool to help parents parse the thousands of names contained in the data for the 2009-10 school year.
DNAinfo does not endorse the accuracy of the ratings, which DOE officials caution was never meant to become public and contain large margins of error.
HOW TO READ THE SCORES:
The scores are based on a complex “value-added” formulas intended to show the extent to which a particular teacher has impacted their students’ achievement on state math and English tests.
The formula compares how students are predicted to score versus their actual achievement after spending a year in a teacher's classroom, taking factors like student attendance and poverty level into account.
An individual teacher’s percentile score represents the percentage of other teachers of the same subject, grade and experience level whose students made less progress. That means that a teacher who scored in the 80th percentile helped students advance more than 80 percent his or her peers did.
Those scores also come with large margins of error, which differ based on how many students a teacher has taught. A teacher who scored in the 80th percentile, for instance, may actually have scored between the 66th percentile and the 90th percentile. DNAinfo included the range of the lowest and highest ends of the margin of error for each teacher in our interactive alongside the headings "Hi" and "Lo."
Teachers were also assigned corresponding ratings by the DOE: "Low" (for scoring below the 5th percentile), "Below Average" (for those who scored in the 5th to 25th percentiles), "Average" (if they scored in the 25th to 75th percentiles), "Above Average" (if they scored in the 75th to 95th percentiles) or "High” (if they scored above the 95th percentile).
While proponents say the value-added method is the most accurate available for predicting the extent to which teachers will improve the tests scores of future classes, the method is also fraught with problems, including massive margins of error that swing as high as 87 percentile points.
The average margin of error for the 2009-10 data's five-year averages, for instance, is 53 percentile points for English teachers and 35 points for math teachers — meaning that a math teacher who scored in the 50th percentile may have actually scored anywhere between 32 and 68 percentile points.
Rates are even higher when only a single year is taken into account.
DOE officials also stress the reports represents just one facet of teacher performance in the classroom.