A pair of experiments at Harvard suggest that students may not be the best judges of how well they're learning. 

A pair of professors split up their introductory physics classes. One half got lectures, and one half got active learning. Then they switched. The professors have a 12 item quiz to measure learning, and also asked students to assess the two types of learning they experienced. The students get better  results after they had done the active learning. But-- they lecture students more strongly agreed with statements like "I feel like I learned a great deal from this lecture" and "I wish all my physics courses were taught this way."

The two professors repeated the experiment the following semester, and found the same results.

There are plenty of caveats here. Harvard freshmen are not exactly a random, representative sampling of students, and a 12 item quiz is not exactly a deep measure of learning. Nor is physics a sample of all kinds of learning content. 

But it reminded me of a story from my teaching day. I taught downstream from one of my colleagues, getting most of my students from her every year. Invariably, when I asked them about their previous English class, they would disparage it (and her) by saying the class was just a lot of fun and games and they never actually learned anything. But then, at the start of every new unit, I'd do formal or informal assessment to see what they already knew. The answer was usually quite a bit.

"Where do you suppose you learned all that," I would ask them, and the light bulb would slowly go on. It took them literally 6-12 months to understand what they had actually learned. 

This phenomenon has several implications for teachers. I think one of the biggest centers on the issue of confidence. 

Part of what a teacher is doing in a classroom is building student confidence, helping them believe that they have the skills and knowledge to handle what comes at them. But it is easy to build confidence that is not rooted in reality, so one of the skills teachers have to foster is the ability to realistically self-assess. 

This kind of self-assessment looks different in different disciplines. A music student has to learn to really listen to both herself and the rest of the ensemble. An artist has to learn to really look at what they're rendering. A writer has to learn to really see what she's written. This is what teacher feedback is about--not just telling the student how she's doing, but giving her the chance to check her own perceptions against those of someone who, ideally, is more expert. 

I've seen plenty of folks in leadership roles pump students up in artificial ways that lead further down the road to crashing and burning. I've seen students blossom early and stall out because they were pumped up with praise. "You are great for an 8th grader," is no help when you're a tenth grader. 

This is one of the big challenges of teaching--to render yourself obsolete for a student who has learned to measure their own growth and skill. And it is a tricky part, to find the line between discouraging truths and overly-positive praise. If you're going to be a life long learner, you have to be able to gauge your own learning accurately. You don't have to look hard to find adults who never learned this lesson. Add it to the list of things they never told you about the job in teacher school.