In the next stage of its effort to block the release of thousands of teacher data reports, the city teachers union is mobilizing educators to scrutinize their reports for errors — even setting up a dedicated phone line to monitor concerns.

Last week, the city announced that it would release a list of teachers’ names and their effectiveness ratings to reporters who had submitted freedom of information requests. The union has sued to stop the release, and the city agreed to postpone publicizing teachers’ names until a hearing is held in court next month.

The union asserts that the ratings should not be made public in part because they are non-finalized and often error-prone internal documents. To make that case, the union is asking teachers to comb their reports for mistakes and tell the union when they find them.

The union sent teachers a sample report showing teachers how to look for mistakes, and has set up a dedicated phone line and e-mail address for concerns about the accuracy of their ratings, according to a memo union President Michael Mulgrew sent teachers last week. A union spokesman said that, as of Friday, at least 200 teachers had called the union to report errors.

Department of Education spokesman Matthew Mittenthal said that the city had seen an increase in the number of calls since the union sent out its memo. But he said that the majority of calls were prompted by misunderstandings of the reports rather than inaccuracies.

Still, Mittenthal said, the city plans to check teachers’ complaints and fix problems it finds before releasing the reports publicly.