Principals can better learn to support an instructional reform when classes for professional development use the new instructional method, giving them a first hand understanding of its effectiveness. Constructivist teaching is supported by the National Research Council's "How People Learn" and the Students at the Center initiative. Students at the Center used constructivist teaching during principal professional development for the Philadelphia school district, to demonstrate its methods and benefits before the principals were asked to support this method for their teachers. It is learner-centered, attempting to engage the learner in actively building new understandings and skills. Assessment includes opportunities for feedback and revision through discussion, papers, or tests. Constructivist classrooms do not look like or sound like the average classrooms. More noise and movement can be a sign that students are emotionally engaged in learning. Students must work in project-oriented groups with self-chosen topics, share with other groups, move around the room, and use manipulative materials. The principals had a very positive reaction. Most participants were struck by how isolated they had felt before the collegiality of the constructivist workshops. They appreciated that information shared did not have to conform to an agenda. Most significantly, they understood from their own experience that assessment of a teacher's classroom could be based on how engaged the students were rather how quietly they were sitting. (Contains 16 references.) (Author/RKJ)