The National Bureau of Economic Research released a study examining two issues:
- Whether value-added (VA) provides unbiased estimates of teachers' impacts on student achievement.
- Whether high-VA teachers improve students' long-term outcomes.
The authors analyzed school district data from grades 3–8 for 2.5 million children linked to tax records on parent characteristics and adult outcomes. They found no evidence of bias in VA estimates using previously unobserved parent characteristics and a quasi-experimental research design based on changes in teaching staff. 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. Teachers have large impacts in all grades from 4 to 8. On average, a one standard deviation improvement in teacher VA in a single grade raises earnings by about 1% at age 28. Replacing a teacher whose VA is in the bottom 5% with an average teacher would increase students' lifetime income by more than $250,000 for the average classroom in the sample. The authors conclude that good teachers create substantial economic value and that test score impacts are helpful in identifying such teachers.