The Magic Number for Value-Added?

IMPACT, the Washington DC teacher evaluation program put in place by Chancellor Michelle Rhee, gives individual value-added measures a 50% weight in teacher evaluation determinations (for teachers who have value-added scores). The magic number for Race to the Top was also 50%. Los Angeles Unified committed to 30% in California’s losing Race to the Top application.

The Economic Policy Institute’s new brief, which details the many concerns with and limitations to current value-added measures, says that 50% is “unwise.” However, despite EPI’s litany of concerns with value-added, the authors, who include Diane Ravitch, Helen Ladd, and Linda Darling-Hammond, conclude that: “Used with caution, value-added modeling can add useful information to comprehensive analyses of student progress and can help support stronger inferences about the influences of teachers, schools, and programs on student growth.”

But if 50% is unwise, what is EPI’s number? The paper doesn’t specify and calls for experimentation among districts. Experimentation is good. But I’d also like to see EPI’s authors and other value-added critics put their best number on the table. I doubt they will, though, because for many, that number is very close to 0%. And defending that number would be much more difficult than pointing out the flaws in value-added.

PS- Important debate note for blog commenters who want to set up straw men: Not even Michele Rhee is implementing a plan where individual value-added measures are used for more than 50% of a teacher’s evaluation. And not even EPI says that value-added measures are useless.