May 13, 2013 at 1:01 am

I’ve written before about computer science pedagogical content knowledge (PCK). Phil Sadler and his colleagues just published a wonderful study about the value of PCK. He found that science teachers need to know science, but the most effective science teachers also know what students get wrong — their misconceptions, what the learning difficulties are, and what are the symptoms of misunderstandings. I got a chance to ask him about this paper, and he said one of the implications of the work that he sees is that he offers a way to measure PCK, and measuring something important about teaching is hard and useful.

For the study described in their paper, Sadler and his colleagues asked teachers to answer each question twice, once to give the scientifically correct answer, and the second time to predict which wrong answer their students were likeliest to choose. Students were then given the tests three times throughout the year to determine whether their knowledge improved.

The results showed that students’ scores showed the most improvement when teachers were able to predict their students’ wrong answers.

“Nobody has quite used test questions before in this way,” Sadler said. “What I had noticed, even before we did this study, was that the most amazing science teachers actually know what their students’ wrong ideas are. It occurred to us that there might be a way to measure this kind of teacher knowledge easily without needing to spend long periods of time observing teachers in their classrooms.”