Seven HISD teachers and the Houston Federation of Teachers union plan to file a federal lawsuit this week over the district’s teacher evaluation system, one of the first nationwide to grade teachers based on students’ test scores.

“This has been a long time coming because we have very miserable members,” said Houston Federation of Teachers president Gayle Fallon.

Fallon declined to release details of the pending lawsuit Tuesday, but she has repeatedly expressed concerns over the statistical method that the district uses to analyze a teacher’s effectiveness. A news release announcing a Thursday press conference about the lawsuit called it “unprecedented.”

The lawsuit is likely to draw national attention as more and more districts move to tie teachers’ pay and job security to student performance. Job evaluations of teachers in the past traditionally have been based on principals’ observations of teachers in their classrooms.

The president of the American Federation of Teachers union, Randi Weingarten, will be in town Thursday for the news conference.

The HISD school board approved the new teacher evaluation system in 2011 but delayed the use of test scores for a year after numerous problems, including computer glitches, confusion among teachers and a lack of appropriate exams to measure student performance.

In a statement Tuesday, HISD said, “We have and will continue to partner with appraisers, teachers, the Houston Federation of Teachers, and the Congress of Houston Teachers to gather feedback regarding the implementation of the HISD teacher appraisal and development system.”