The Most Important School Factor: The Teacher
I always tell soon-to-be teachers that the teacher is the most important school factor in student achievement. Now comes more research data to back me up. David Leonhardt in the NYT reports on a study by Harvard economist Raj Chetty.
Early this year, Mr. Chetty and five other researchers … examined the life paths of almost 12,000 children who had been part of a well-known education experiment in Tennessee in the 1980s. The children are now about 30, well started on their adult lives.
Just as in other studies, the Tennessee experiment found that some teachers were able to help students learn vastly more than other teachers. And just as in other studies, the effect largely disappeared by junior high, based on test scores. Yet when Mr. Chetty and his colleagues took another look at the students in adulthood, they discovered that the legacy of kindergarten had re-emerged.
Students who had learned much more in kindergarten were more likely to go to college than students with otherwise similar backgrounds. Students who learned more were also less likely to become single parents. As adults, they were more likely to be saving for retirement. Perhaps most striking, they were earning more.
All else equal, they were making about an extra $100 a year at age 27 for every percentile they had moved up the test-score distribution over the course of kindergarten. A student who went from average to the 60th percentile — a typical jump for a 5-year-old with a good teacher — could expect to make about $1,000 more a year at age 27 than a student who remained at the average. Over time, the effect seems to grow, too.
The study aimed to help determine whether teachers had an effect on students’ success. And the Tennessee project offered the same kind of data that other researchers have used to measure the effect of good charter schools.
The Tennessee experiment, known as Project Star, offered a chance to answer these questions because it randomly assigned students to a kindergarten class. As a result, the classes had fairly similar socioeconomic mixes of students and could be expected to perform similarly on the tests given at the end of kindergarten.
Yet they didn’t. Some classes did far better than others. The differences were too big to be explained by randomness. (Similarly, when the researchers looked at entering and exiting test scores in first, second and third grades, they found that some classes made much more progress than others.)
Class size — which was the impetus of Project Star — evidently played some role. Classes with 13 to 17 students did better than classes with 22 to 25. Peers also seem to matter. In classes with a somewhat higher average socioeconomic status, all the students tended to do a little better.
But neither of these factors came close to explaining the variation in class performance. So another cause seemed to be the explanation: teachers.
Some are highly effective. Some are not. And the differences can affect students for years to come.
Amen.
