NASHVILLE (AP) — The state's largest teachers union has filed a federal lawsuit challenging the constitutionality of the state's use of standardized test scores to evaluate teachers.

The lawsuit filed Thursday in Nashville says more than half of the public school teachers in Tennessee receive evaluations that are based substantially on standardized test scores of students in subjects they do not teach. The Tennessee Education Association and other plaintiffs want the practice stopped.

The TEA has long argued that the Tennessee Value-Added Assessment System, or TVAAS data, shouldn't be relied upon because it's a statistical estimate and could lead to a flawed evaluation of a teacher.

Last year, state lawmakers passed legislation that prohibits standardized test scores from being tied to teacher licensing. Gov. Bill Haslam signed the measure.