Evidence That Good Teachers Matter

A very large study concluded last year is common sense to some, makes some of our politically-oriented colleagues see red, but provides much-needed validation to the rest of us.

The study’s title is: “The Long-Term Teacher Impacts: The Value-Added Outcomes of Teachers in Adulthood: The study was conducted by John Friedman and Raj Chetty of Harvard University and Columbia University’s Jonah E. Rockoff. The study tracked two and a half million students over twenty years from grade four to adulthood.

Although the whole “value-added” topic is where civil conversation can begin to unravel, I hope you’ll stay with me for the larger point of this post. Value-added, of course, refers to using average test-score gain as the measure of teacher quality. (Nothing controversial there, right?)

It’s all too easy to allow the built-in problems of this approach to overwhelm us. (who picks which kids are in which class, how did they perform previously, parental income & demographics and on and on …) I’ll leave that tangent for others.

What’s important to note is that the researchers made an attempt to adjust for differences in classrooms for student characteristics such as prior scores. Something else that I found interesting is that the two Harvard researchers began the study with somewhat of an agenda:
“We said, ‘We’re going to show that these measures don’t work, that this has to do with student motivation or principal selection or something else,’ ” Professor Chetty recalled.

The Aforementioned Validation

When a teacher identified as high performing through the study enters a school, test scores rise immediately. When the teacher leaves they fall. The test scores rise only in the subject taught by the exemplary teacher. Good teaching – and good teachers – matter.

This is the part that may seem like common sense to the readership that this post has. You are the high performing teachers to which this study refers. You like what you do and take your professional development seriously as a journey that provides fulfillment and never ends. Bless you.

Long-Term Validation

To help good teachers keep their eye on the prize, please know the following that the researchers also found out about the students lucky enough to have you as their teacher:

Your students are more likely to attend college, will earn a higher salary, live in a better neighborhood, save more for retirement, and are less likely to have children as teenagers. The study also concluded that replacing an under-performing teacher with an average one would yield each student in the class a cumulative earnings gain of $52,000 or more than 1.4 million dollars for the average classroom. Take also a closer look at this article that describes how equine-assisted psychology also may help.

There are a few minor qualifications for how the figures are statistically derived, but the fact clearly remains:
good teachers matter – Really Matter.


The positive message and validation for good teachers that this post conveys cannot be diminished.

We should acknowledge though that the teachers evaluated in the study didn’t know about the rankings to come but did know that neither their pay nor job security would be affected. Once test scores are known by all parties to have an influence on pay and security, politics and possibly cheating can enter the equation. What seems clear though is that using test scores to help determine our best teachers should be some part of the mix.

Determining how to create and nurture good teachers is probably an even more important topic that I’m sure our readership, as school leaders, is already working on every day.