Laying out its case for why the courts should stop the Bloomberg administration from releasing teacher effectiveness ratings, the city teachers union described the ratings as internal, incomplete, and riddled with flaws

The union is trying to block the city from releasing the names and ratings of nearly 12,000 teachers, arguing that releasing them would be an invasion of teachers’ privacy.

The bulk of the materials filed today were prepared by United Federation of Teachers researcher Jackie Bennett and are intended to show that the data reports are inaccurate.

“The UFT’s review of the TDR’s has revealed that a large portion of the reports received are materially flawed as they have been calculated based on errors in student lists,” Bennett writes.

“In addition, most of the flaws identified came from the most recent year’s TDRs, for which information was slightly less opaque and memories were fresher,” she continues. “Yet, the TDRs contain three more years of historical student lists and information, lumped in aggregate numbers. The UFT found it very difficult, if not impossible, to penetrate that information, even in a superficial manner.”

The union has been encouraging teachers to report errors on their reports since city officials announced in October that they intended to release the reports publicly. To support Bennett’s argument, the union filed nearly 20 examples of individual data reports that it says show errors.

The union also filed affidavits today from two academic experts on testing and evaluation — Henry Braun of Boston College and Derek Briggs of the University of Colorado, Boulder — who argue that the value-added model used by the city does not accurately measure teacher effectiveness.

“Although TDRs may have a role as a quantitative component in the enhancement of teacher performance, their usefulness is limited and they certainly should not be utilized to make direct causal attributions of teacher effectiveness,” Braun writes.

The city has argued in its own court filings that the data reports are records of teachers’ performance as public employees, and thus teachers do not have the right to keep them private. Five news organizations have joined the city to argue that the reports are not protected by the Freedom of Information Law.

The city and union are expected to make their cases before a Manhattan judge on Wednesday.