Even those the city teacher scores released Friday take into account tons of variables, like students' demographics, they still may not give a complete picture of student performance. NY1's Courtney Gross filed the following report.
New Yorkers might want to take the scores of 18,000 public school teachers released Friday with a grain of salt.
"It may not reflect what you're really trying to measure. It's just one data point and there are lots of data points," said Mayor Michael Bloomberg.
For the first time, the city has released thousands of scores evaluating teachers, names included, for school years 2007 through 2010. But those numbers are open to interpretation.
The average margin of error for English teachers is 53 percentage points. For math teachers, it is 35 percentage points.
Given that spread, experts questions how seriously the scores should be taken.
"It's a very imprecise measure of teacher effectiveness. It makes it difficult to make comparisons between teachers," said Sean Corcoran of New York University.
Nonetheless, they can still be telling.
Over the three years of data, 696 teachers were constantly in the high performance category and 521 were consistently in the low performance category.
But elsewhere, consistencies are few and far between. According to the Department of Education, there is no relationship between a school's demographics and the number of teachers with the highest scores.
P.S. 122 in Queens, for example, serves a less needy population and has the most teachers in the 99th percentile.
Compare that to P.S. 86 in the Bronx, where 82 percent of students there qualify for a free lunch and 20 percent have special needs. They are tied for the most teachers in the top five percent.
Of the 10 schools where 99 percent of students qualify for free or reduced-cost lunches, six of them had at least half of their teachers ranked below average.
Those schools were P.S. 22 in Brooklyn, I.S. 303 Herbert S. Eisenberg, P.S. 163 Arthur A. Schomburg, P.S. 230 Dr. Roland N. Patterson, P.S. 55 Benjamin Franklin and P.S. 120 Carlos Tapia.
Some of those teachers at those schools were new and only had data for one year.
One P.S. 22 parent said, "That's shocking that this school has teachers in the lower percentile. That's a real shock to me."
All in all, these numbers might not amount to much. After all, a quarter of these teachers no longer work for the city.