Guest view: Are test scores true measures of good teachers?
The tabloid front page blared its sensational headline (New York Post, 2/25) "Revealed: Teacher Grades." It sounded like exactly what it was: published test scores linked to individually- named New York City teachers, totaling 12,170. But, what do "value-added" scores reveal?
Variables in the computation of each teacher's individual or "value added" scores, includes poverty index, numbers of limited English Language Learners (ELL), special education kids, students of color, etc. The report looks at test results in mathematics and reading from the previous year, predicting an expected level of achievement for each student. A teacher's "value-added" rating is the difference between predicted and actual student achievement on math and reading tests.
Are "value-added" ratings simple, logical, assertive and true in their assessment of a teacher's effectiveness in a classroom? Eminent education historian, Diane Ravitch, a professor at New York University, former Assistant Secretary of Education under President George H. W. Bush, disagrees. In a recent NY Review of Books blog, Ravitch wrote, "Most testing experts believe that the methods for '