Study: Great teachers have lifelong impact

Students with an excellent elementary or middle-school teacher don’t just earn higher reading and math scores, concludes a new study that tracked one million students in an urban district over 20 years. A single year with a high value-added teacher leads to higher college attendance, higher adult earnings and even lower teenage-pregnancy rates, according to the authors, economists Raj Chetty and John Friedman of Harvard and Columbia Professor Jonah Rockoff.

All else equal, a student with one excellent teacher for one year between fourth and eighth grade would gain $4,600 in lifetime income, compared to a student of similar demographics who has an average teacher. The student with the excellent teacher would also be 0.5 percent more likely to attend college.

It may be difficult to hire more excellent (top five percent) teachers, but it’s not necessary.

. . . the difference in long-term outcome between students who have average teachers and those with poor-performing ones is as significant as the difference between those who have excellent teachers and those with average ones, the study found.

It adds up: Replacing a low-value-added (bottom five percent) teacher with an average teacher would raise a single classroom’s lifetime earnings by about $266,000, the economists estimate.

“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,” said Professor Friedman, one of the coauthors.

. . . “The message is to fire people sooner rather than later,” Professor Friedman said.

When a high value-added teacher transferred to a new school, student performance went up in the grade or subject area taught by that teacher, matching predicted gains. Scores dropped in the school the high-value teacher had left. Conversely, scores went up significantly when a low-value teacher left and dropped in her new school.

High performing teachers may more than justify much higher pay,” Slate observes.

“Great teachers create great value – perhaps several times their annual salaries,” write the authors. Now a working paper, the study will be submitted to a journal.

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