Throughout the book I’ve mentioned moments that got my attention. Most involved learning about student understandings during class discussions or interviews. Reading the article, “Educating Hannah: It’s a What?” provided another one of those attention-getting moments. In the article, Cockcroft and Marshall (1999) describe a conversation between two sisters.

“Oh gosh!” said Hannah. “You’ve been completely misled if you think there are thick and thin plane shapes.”

(p. 327)