Professor Bill Brett was a wonderful lecturer. He filled the blackboard with meaningful and organized notes. Then, while erasing the board, he asked us questions.

Somehow he could always detect who had not paid attention or who did not understand.

Since I was a “field kid” growing up, I knew a lot of biology. So I never got called on!

One day he was explaining clam shells and bone tissue. He got to the end of the blackboard and asked “Where would I find an example of calcium carbonate?” as he began erasing.

So, I diverted my eyes downward and avoided his gaze as he scanned the class.

“Mr. Schrock”—he called on me!

“The chalk in your hand, sir,” I crisply replied.

The immediacy of my reply caught Dr. Brett off guard. For a moment, he stopped erasing.

“You did that to me,” he smiled.

“Yes, sir,” I confessed.

The rest of the class did not have the least idea what we were talking about. I had baited him to call on me.

Have you ever wondered how teachers can always pick out the student in class who does not know the answer?

Yes, it is the eyes.

Today, when I visit student teachers, I do not sit at the back of class to watch them. And I don’t want a videotape of them teaching. I sit forward enough in class that I can look back and see what the teacher is responding to. How many kids are getting “Ah ha’s” in their eyes, as they now understand something that they formerly did not. How many students eyes show they are totally lost. “Huh?” is also obvious in their eyes? And do my student teachers then use this information to adjust their explanation on the spot. Perhaps they call upon a student whose eyes show that they do know, to re-explain for those who do not?

Teachers can “read eyes” back five or six seats in each row. That is what makes a regular classroom very efficient. But students sitting in a large lecture hall beyond those first five rows might as well not be there. Unable to see the students’ eyes, the teacher cannot adjust the message to be sure those distant students understand the message.

Distance learning? Same problem. Not enough resolution. When time-consuming feedback mechanisms have to be used, the efficient flow of the message and the group train of thought are lost.

There is science behind this skill. Fifty years ago, in the April 1965 Scientific American, Eckhard Hess described how pupil size revealed ongoing mental activity in “Attitude and Pupil Size.” Using the technology of that time, his experiments measured how pupil response “is a measure of interest, emotion, thought processes and attitudes.” Just airbrushing the pupils on a girl’s photo made a dramatic difference in male’s judgements; large pupils revealing interest while small pupils meant no date tonight.

They extended this to spelling and math problems. Recite a simple math problem to a person—a problem they can do in a few seconds in their mind—and watch their eyes. Their pupils dilate as they work it out and the split second they arrive at the answer but just before they say it, the pupils constrict.

As Aristotle said millennia ago, the eyes are the windows to the mind.

I describe this art of teaching and the instantaneous reading of students’ eyes because there are new digital education fads that claim to be a breakthrough in evaluating whether students are learning. Similar to most digital distractions, they ignore current good teaching practices and offer a poor substitute at many times the cost.

Customized online evaluation systems are now being hawked to universities and public schools to provide feedback from students. But it is a day late and costs dollars more.

But any parent who wants to really know their child’s understanding has always been able to determine that in a few seconds, and for free.

Similar to good teachers, they just say: “Look me in the eye and tell me.”