Key Coverage

Evaluating New York Teachers, Perhaps the Numbers Do Lie

You would think the Department of Education would want to replicate Stacey Isaacson — a dedicated teacher who has degrees from the University of Pennsylvania and Columbia and works long hours every school day — and sprinkle Ms. Isaacsons all over town. Instead, the department’s accountability experts have developed a complex formula to calculate how much academic progress a teacher’s students make in a year — the teacher’s value-added score — and that formula indicates that Ms. Isaacson is one of the city’s worst teachers.