Every day for the last four years, Leah Alcala has greeted her Berkeley, California, middle-school students with an exercise [1] she calls “my favorite no,” the Huffington Post reports. As students enter class, they see a math problem on the whiteboard and are instructed to solve it on index cards. After they finish, Alcala immediately sees which answers are right or wrong — “yes” and “no” — and chooses her favorite incorrect response, the one most liable to be repeated. She then explains the mistake to the class — never identifying its culprit — and demonstrates how it can be avoided.
“At this point, I can almost predict the mistakes they’re going to make in a way that I never used to be able to,” Alcala says. In addition to helping her students understand that “mistakes are natural,” she says, she has seen their test scores rise since she started the activity…