William Sanders

Father of TVAAS

New York

Integral to "value-added" is a requirement that some score low

Add one more point of critique to the city’s Teacher Data Reports: Experts and educators are worried about the bell curve along which the teacher ratings fell out. Like the distribution of teachers by rating across types of schools, the distribution of scores among teachers was essentially built into the “value-added” model that the city used to generate the ratings. The long-term goal of many education reformers is to create a teaching force in which nearly all teachers are high-performing. However, in New York City’s rankings — which rated thousands of teachers who taught in the system from 2007 to 2010 — teachers were graded on a curve. That is, under the city’s formula, some teachers would always be rated as “below average,” even if student performance increased significantly in all classrooms across the city. The ratings were based on a complex formula that predicts how students will do — after taking into account background characteristics — on standardized tests. Teachers received scores based on students’ actual test results measured against the predictions. They were then divided into five categories. Half of all teachers were rated as “average,” 20 percent were “above average,” and another 20 percent were “below average.” The remaining 10 percent were divided evenly between teachers rated as “far above average” and “far below average.” IMPACT, the District of Columbia’s teacher-evaluation system, also uses a set distribution for teacher ratings. As sociologist Aaron Pallas wrote in October 2010, “by definition, the value-added component of the D.C. IMPACT evaluation system defines 50 percent of all teachers in grades four through eight as ineffective or minimally effective in influencing their students’ learning.”