Highly Effective Teachers Have Long-Term Impacts on Students, Study Suggests

An education study co-authored by two Harvard professors found that top teachers increase students' lifetime income and standard of living, confirming the commonly-held belief that a single teacher can transform a student’s life.

According to the study, high value-added teachers—or those in the top 5 percent as measured by test scores—produce students who are more likely to attend college, earn higher salaries, live in better neighborhoods, and save for retirement. The students are also less likely to get pregnant as teenagers.

The study, titled “The Long-Term Impacts of Teachers: Teacher Value-Added and Student Outcomes in Adulthood,” was published in December by Economics professor Raj Chetty and Kennedy School assistant professor John N. Friedman and Jonah E. Rockoff of Columbia.

The research examined 18 million 3rd through 8th grade test scores in English and math drawn from 1989 to 2009 and compared the data with tax records to determine outcomes. A teacher’s “value-added” was determined by averaging his or her test score gains during the academic year, and the scores were adjusted for differences such as students’ previous scores.

The data was obtained from a large, diverse public school district that encompasses neighborhoods of differing socioeconomic statuses, Friedman said.

The research suggests that value-added assessments of teachers effectively predict long-term outcomes.

According to the study, “Replacing a teacher whose VA is in the bottom 5 percent with an average teacher would increase the present value of students’ lifetime income by more than $250,000” on average.

“If you’re concerned about growth, especially in a global economy, you’re concerned about making U.S. workers competitive,” said Chetty. “Investing in education, especially at the elementary level, makes a lot of sense.”

The study’s findings add to the debate over education spending and reform.

Friedman said that teachers should be evaluated like other high-earning professionals.

“If we want to pay teachers $100,000, we should treat them like people in other professions that are getting paid six figures,” he said. “We should evaluate performance, we should give feedback, we should improve them as much as possible, we should richly reward those who are successful, and we should improve performance among those who are not doing so well.”

Yet Friedman noted that test scores not the only means of evaluation.

He suggested combining tests scores “with other things like principal evaluation, classroom observation, peer evaluation, and student evaluation” in order “to put together as rich and as accurate a picture of each teacher as you can.”

The study’s findings have attracted significant attention, and was the subject of a column in the New York Times by Nicholas D. Kristof '81-'82.

Allison R. Kimmel '12, Director of Advocacy at Harvard Students for Education Reform, said the study shed light on the importance of effective teachers.

“People don’t realize that teachers have these long-term effects on students,” Kimmel said. “We think that teachers matter for one year to make sure students master content, but great teachers are able to affect people’s lives long after they leave the classroom.”