Following up on the article we shared last week on the value-added approach to teacher evaluation in Washington, DC, a recent New York Times article, along with a column by Nicholas Kristof, report on a new study that examines whether the value-added approach effectively distinguishes between good and bad teachers, and how much impact those teachers have on students.

After tracking 1 million students over 20 years, the authors concluded that 1) value-added approaches accurately measure teacher quality over time, and 2) students of teachers with high value-added scores were subsequently more successful in many dimensions, including attending college, earning higher salaries, and avoiding teenage pregnancy.

In the words of one of the co-authors, John N. Friedman of Harvard University: “If you leave a low value-added teacher in your school for 10 years, rather than replacing him with an average teacher, you are hypothetically talking about $2.5 million in lost income.”Kristof concludes that “The obvious policy solution is more pay for good teachers, more dismissals for weak teachers.”

Use the value-added tag to access previous PREAL analyses of value-added ratings.