Ok, the title of my blog post does a disservice to the sophisticated study of teacher quality produced by researchers from Harvard and Columbia universities.
A December 2011 National Bureau of Economic Research (NBER) study by Raj Chetty, John N. Friedman, and Jonah E. Rockoff, “The Long-Term Impacts of Teachers: Teacher Value-Added and Student Outcomes in Adulthood,” concludes that value-added measures are pretty good indicators of teacher quality. According to the authors,
Replacing a teacher whose VA [value-added] is in the bottom 5% with an average teacher would increase students’ lifetime income by more than $250,000 for the average classroom in our sample. We conclude that good teachers create substantial economic value and that test score impacts are helpful in identifying such teachers.
Value-added is a statistical technique that measures student test score changes from point A to point B. The difference between the two points is the “value” that a teacher adds to his or her students.
North Carolina already has a value-added system (called EVAAS) available to public school administrators and staff, but parents do not have access to the system. Public schools do not want anyone to know that Johnny and Susie’s teacher can’t teach!
Performance pay is another useful application of value-added measures. School districts can compare the value-added scores of teachers regardless of the level of students they teach. This is important because it neutralizes the advantage of teaching classes of advanced students. Value-added measures the progress of individual students, which is much different than (and superior to) the current method of reporting proficiency levels or scale scores by school. In this way, teachers who made great progress with low-performing students would be paid more than a teacher who made few gains with high-performing kids. Absent a value-added system, a school district would likely reward the latter teacher.
