One of my favorite far side cartoons features Rex the Wonder Dog. Rex is shown balancing an elaborate array of objects while traversing a tightrope on a unicycle. The caption reads, “High above the hushed crowd, Rex tried to remain focused. Still, he couldn't shake one nagging thought: He was an old dog and this was a new trick.” Maybe that cartoon speaks to you the way it does to me. As one of the developers of the middle-grades curriculum Mathematics in Context (MiC), one of the Standardsbased middle school curriculum projects funded by the National Science Foundation, I have used that cartoon many times to describe to teachers, young and old, how it might feel to be a teacher who is about to implement a mathematics curriculum such as MiC. I can usually tell from the nervous laughter that although they might not be old, they recognize that the new Standards-based curricula will require them as teachers to learn “new tricks.”