Do great teachers exist?

This probably seems like a dumb question. In fact, everyone I’ve asked this to thinks this is a dumb question. This might seem even dumber given that I’m a professional tutor, and I’ve taught literally thousands of students in classrooms and online.

But before the entire world yells at me, let me start off with an anecdote, as these sorts of essays tend to start. In their last few years of high school, my brothers had a wonderful calculus teacher, Mrs. D. She was kind, warm, and taught them a lot about math. My brothers consider her a great teacher.

Two years after them, I had Mrs. D. She was the end of her teaching career (literally, I was in her last class), and in her 80s. By random chance, my class was filled with stoners who continually derailed the class with high thoughts. Mrs. D quickly gave up on teaching and we had no tests or homework for the entire year. I had to teach myself the entirety of AP BC Calculus in the last month or two of the year.

Mrs. D was not a great teacher for me. She was for my brothers. Ultimately, this didn’t seem to matter, as my brothers and I all got into excellent colleges, did okay in said colleges, and now are in knowledge-based white collar careers. Point in favor of no consistently great teachers, right? Let’s take it one step further.

I actually ended up getting a 5 on the AP Calc exam, the same score as my brothers. Not only did Mrs. D not affect our life trajectory, she didn’t even affect our ultimate knowledge of calculus.

So Mrs. D, to recap, would be considered a great teacher by the experience of my brothers, but not by my experience. And yet, my brothers and I have very similar outcomes in calculus, school achievement, and life. What, therefore, would my brothers mean if they called Mrs. D a great teacher? More broadly, are there great teachers, by any definition?

Let’s actually tackle the latter first, then get back to the former. You’ll see what I mean.

Statistics on and measurements of teachers

I’m going to start with a few graphs (and a lot of thanks to SlateStarCodex for this portion and for a much deeper dive into the literature than I want to do):

These are results from comparison studies. Essentially, we look at the difference between teachers in different schools. These studies show that only 5 to 20% of the difference in test scores between students can be explained by their teacher. Or, in other words, given clones of a kid and clones of a school, you would see a 5% to 20% difference in the clones’ test scores.

Of course, this is averaging together many teachers and schools, so maybe this isn’t the best comparison. What if we only look at the compounding effects of many excellent teachers, or many bad teachers?

Well, this is where Value Added Modeling (VAM) comes in. In VAM, we try out assigning kids to a series of excellent teachers, or a series of poor teachers, and we see how they do. It turns out that students can improve markedly with a series of excellent teachers, or do very poorly with poor teachers. Score one for great teachers!



Maybe, but not so fast. Unfortunately, how we figure out who the excellent teachers are is complicated. It’s supposed to be “whoever’s students’ test scores improve the most during the year”. But that’s something that, according to the pie charts above, can be affected a lot by non-teacher factors. So, just because a teacher’s students don’t improve, doesn’t meant that it’s the teacher’s fault.

In other words, maybe it’s a mistake to even try identifying excellent teachers in the first place. Maybe it’s not. It’s a huge debate.

The answer to resolving this debate currently seems to be yelling at each other, then yelling at Betsy Devos. So this probably isn’t a great rabbit hole to go down.

Instead, I want to take this a different route. It seems obvious to me that terrible teachers exist. For instance, if your teacher screeches continually every 30 seconds and does nothing else (and is, in fact, a fire alarm), you will almost certainly learn nothing for the year. Or, alternatively, if your teacher doesn’t show up, you will also probably learn nothing.

But a great teacher doesn’t just seem to be the opposite of a terrible teacher. They seem to be someone who will literally change your life, not just improve your test scores. Maybe I watch too many movies, but in Stand and Deliver, the teacher literally takes students from not knowing multiplication tables to learning calculus in a year. In Dead Poet’s Society, Robin Williams gets a kid to discover his love of theater and become an actor, changing the course of his life.

We know that adopted parents have a hard time affecting their children’s lives. In fact, adopted children seem to have a far harder time on schoolwork than other children, even though adopted parents tend to be wealthier and more educated than the average parent.

So if adopted parents have a tough time molding their kids, can one year with a teacher really change the course of your life? Well, only one way to find out. Back to anecdotes!

Anecdotes on teachers who changed people’s lives

People don’t think of statistics on test scores when they think of great teachers. They think of their own life, and of stories they read. People love stories.



For example, when I Google “teachers who changed your life”, I get:

This soppy article , written to an anonymous teacher whose classroom was a safe space Chad Adlis , talking about how his 4th grade teacher inspired him to become the first person in his family to graduate from high school, then college, then law school Bill Gates , discussing how the school librarian introduced him to a world of books in 4th grade (which is apparently an important year) Lev Raphael , whose creative writing teacher inspired him to become a professional writer

A lot of inspiring stories. Literally none of them are about how much these people actually learned in any individual class, especially not as measured on a standardized test. Weirdly enough, not even Bill Gates, whose foundation pushes standardized tests.

So what gives? For one thing, maybe nobody cares how much they actually learned in 3rd grade math or reading. If you don’t learn it in 3rd grade, it’s pretty easy to pick it up in 4th grade. And it really doesn’t matter if you learn the section on clouds (cumulonimbus FTW), so nobody remembers how well they were taught that.

Also, it’s pretty hard to do counterfactuals for most people, especially about our own lives. Bill Gates, for instance, is a very intelligent, driven person from a wealthy, educated family. I have no doubt he has fond memories about Mrs. Caffiere, but it seems unlikely that he would have never graduated beyond sci-fi books without her.

To briefly go back to statistics, some authors calculated that 75% of educational attainment is genetic. We can assume that some large percentage of the remaining 25% is family and home life. Where can an individual teacher’s influence come in?

A case for redefining teacher training

If I’m right, then there probably are not great teachers. There are not teachers who can consistently make students learn drastically more than the average teacher for the same subject. There also are not teachers who can change the course of a student’s entire life.

Teachers can improve in their teaching, of course, and compounding effects of above-average teachers matter. So, I’m not saying throw out the entire idea of teaching altogether, or of improving teachers.

But I am saying something else. When we think of great teachers in our own lives, we think of those who were warm, caring, and expected the best out of us. In other words, they made us feel good.

In that case, why do we not train for that, or at least select for it? If all we remember from our fourth grade teachers was who made us feel good, then it would seem to be beneficial to select for and optimize feel-good techniques from fourth grade teachers.