In their study entitled The Long-Term Impacts of Teachers: Teacher Value-Added and Students’ Outcomes in Adulthood
, Raj Chetty and John N. Friedman from Harvard and Jonah Rockoff from Columbia pose the question: “Is teacher value-added a good measure of teacher quality?” Their report analyses the “value-added” (VA) approach, which rates teachers based on their students’ test score gains. A teacher's VA is defined as the average test-score gain for his or her students, adjusted for differences across classrooms in student characteristics (such as their previous scores).
The VA question has sparked debate largely because of disagreement about (1) whether VA provides unbiased estimates of teachers’ impacts on student achievement and (2) whether high-VA teachers improve students’ long-term outcomes.
The researchers analyzed school district data from grades 3-8 for 2.5 million children linked to tax records on parent characteristics and adult outcomes. Their report abstract states that students assigned to high-VA teachers are more likely to attend college, attend higher ranked colleges, earn higher salaries, live in higher SES neighborhoods, and save more for retirement. They are also less likely to have children as teenagers. On average, having such a teacher for one year raises a child's cumulative lifetime income by $50,000 (equivalent to $9,000 in present value at age 12 with a 5% interest rate). They propose that the earnings gains from replacing a low value-added (bottom 5%) teacher with one of average quality grow as more data are used to estimate VA.
The researchers conclude that good teachers create substantial economic value and that test score impacts are helpful in identifying such teachers.
To view the report, charts, presentation slides, and a video of the presentation, visit http://obs.rc.fas.harvard.edu/chetty/value_added.html.