Four core principles should guide the professional development of teachers:

1. Make sure that the teacher evaluation system has the capacity to drive professional development.
2. Professional development should be structured as a collaborative effort by a group of teachers answering DuFour’s critical questions: what do we want students to learn, how will we know they’ve learned it, and what will we do if they don’t?
3. Look as much as possible to the expertise, talent, and skills of teachers working with teachers as the most sustainable form of professional development.
4. Use external consultants for new undertakings where internal expertise may be lacking, but have a plan for growing that expertise.