We continue our discussion about just how valuable a good teacher is by taking a look at a recently published study by Harvard’s Raj Chetty and John N. Friedman and Columbia ‘s Jonah E. Rockoff that followed one million students from the fourth grade to adulthood and, according to the Times’ Nicholas Kristof, reached the following conclusions:
Having a good fourth-grade teacher makes a student 1.25 percent more likely to go to college, the research suggests, and 1.25 percent less likely to get pregnant as a teenager. Each of the students will go on as an adult to earn, on average, $25,000 more over a lifetime — or about $700,000 in gains for an average size class — all attributable to that ace teacher back in the fourth grade. That’s right: A great teacher is worth hundreds of thousands of dollars to each year’s students, just in the extra income they will earn.
The study, by economists at Harvard and Columbia universities, finds that if a great teacher is leaving, parents should hold bake sales or pass the hat around in hopes of collectively offering the teacher as much as a $100,000 bonus to stay for an extra year. Sure, that’s implausible — but their children would gain a benefit that far exceeds even that sum.
Conversely, a very poor teacher has the same effect as a pupil missing 40 percent of the school year. We don’t allow that kind of truancy, so it’s not clear why we should put up with such poor teaching. In fact, the study shows that parents should pay a bad teacher $100,000 to retire (assuming the replacement is of average quality) because a weak teacher holds children back so much.
What shone through the study was the variation among teachers. Great teachers not only raised test scores significantly — an effect that mostly faded within a few years — but also left their students with better life outcomes. A great teacher (defined as one better than 84 percent of peers) for a single year between fourth and eighth grades resulted in students earning almost 1 percent more at age 28.
Suppose that the bottom 5 percent of teachers could be replaced by teachers of average quality. The three economists found that each student in the classroom would have extra cumulative lifetime earnings of more than $52,000. That’s more than $1.4 million in gains for the classroom.
Now, how to define, and effectively measure, great teaching.
(Kristof’s column, “The Value of Teachers,” appeared in Thursday’s New York Times.)