She got it wrong, but why?

You know when your students get something wrong, but do you know why they get it wrong? Figuring out a student’s cognitive missteps is one of the most difficult parts of this job — and one of the keys to being an effective teacher.

It starts with a question for the class. Let’s take one day in Macroeconomics. I’ve explained to students how the consumer price index is calculated. They have practiced with partners doing calculations using different base years.

I ask: If we pick 1990 as the base year, instead of 1982-84, will we get a different inflation rate?

I scan the room, selecting who to cold-call. I don’t want to pick someone who definitely knows. I don’t want to embarrass anyone either. I want to pick someone who might know, who is working through the problem. I choose a quiet girl who is staring at her notes, seeking answers.

She says, “Yes?”

The answer is no. How to respond?

As a new teacher, I used to try to coax their wrong answers into right answers, to help them save face. I’d say something like, “Well, it’s true that our CPI index numbers would be different…” Or I’d simply turn to another student, one I was confident had the correct answer.

Neither strategy is all that helpful to this student, who I’ll call Amy. Amy has reasoned through this question, and somehow she has arrived at the wrong answer. Let’s imagine that instead of calculating the CPI, she was learning how to walk from her house to the local CVS.

If she shows up at the wrong place (Walgreens), and I tell her she was sort of at the right place, I’m not fooling anyone. And if I (or a classmate) just tell her she is in the wrong place, that doesn’t help her find the CVS next time.

There are dozens of ways to go wrong in calculating the CPI. Maybe her multiplication was wrong, and she actually got different numbers. Maybe she doesn’t know how to calculate percentage change. Maybe she’s really stuck on the concept of index numbers.

The point is: I won’t know if I don’t ask. According to the authors of Make it Stick, teachers often suffer from the “curse of knowledge.” We find out subject matter so easy and obvious that we can’t put ourselves in the shoes of students who are just starting out and struggling.

If we can no longer imagine ourselves in the students’ shoes, then we need them to put us there, to tell us what it looks like from their perspective and help us feel their frustration.

If I want to help Amy learn, I have to understand where she took a wrong turn, so she can correct for it.

A better response? Ask Amy: How did you decide the CPI would be different? See if other students agree with her and can explain their thinking. Get all the misunderstanding out on the table. Don’t focus on the right answer, but on the learning process.

Not only will she learn how to calculate the CPI, but she’ll learn that making mistakes isn’t so bad if you can learn from them. What could be a better lesson than that?