The method is known as “value-added modeling,” or VAM, and it purports to be able to use student standardized test scores to determine the “value” of a teacher while factoring out every other influence on a student (including, for example, hunger, sickness, and stress). One way it works is by predicting, through a complicated computer model, how students with similar characteristics are supposed to perform on the exams, and teachers are then evaluated on how well their students measure up to the theoretical students. New York is just one of the many states where VAM is a key component of teacher assessment. Evaluation experts have warned policymakers that this method is not reliable for evaluating teachers, but VAM became popular among school reformers as a “data-driven” evaluation solution.

Lederman’s suit against state education officials — including King — challenges the rationality of the VAM model, and it alleges that the New York State Growth Measures “actually punishes excellence in education through a statistical black box which no rational educator or fact finder could see as fair, accurate or reliable.”

Here’s what happened to Lederman: In 2012-13, 68.75 percent of her New York students met or exceeded state standards in both English and math. She was labeled “effective” that year. In 2013-2014, her students’ test results were very similar, but she was rated “ineffective.” Meanwhile, her district superintendent, Thomas Dolan, declared that Lederman — whose students received standardized math and English Language Arts test scores consistently higher than the state average — has a “flawless record.”