The authors examined the characterization of mathematical knowledge of teachers using educative curriculum materials. In particular, they investigated knowledge of change and rate of change (in the context of algebra and functions) of 12 teachers with differing levels of experience. Participants used a same set of curriculum materials that embed features that had potential to be educative for teachers. Data were collected using a mathematical task-based interview. The analyses suggest that context played an important role with regard to teachers' ability to explore complex situations. Teachers with a high level of experience teaching the educative curriculum materials showed greater success in dealing with complex problems and recognizing similar and contrasting characteristics of different types of representations across contexts. The findings suggest that curriculum materials can be designed to assist teachers' learning in ways that contribute to establishing contexts where teacher learning takes place.