Developing content knowledge through professional development grounded in the practice of teaching This strategy employs (a) rich tasks selected in an area that teachers recognize as a weakness in their preparation to teach, that they can try in their own classroom, that contain extensions beyond what students would be expected to do, and (b) occasions where teachers can work independently and with others to discuss ways of reasoning about problems, justifying approaches and solutions, and analyzing carefully selected pieces of student work that have the potential to push at teachers' own knowledge.

Learning from mistakes and misconceptions: PD materials include tools that help teachers diagnose their own misconceptions by asking them to analyze those in examples of student work.