This study explores Knowledge Building as a principle-based innovation at an elementary school and makes a case for a principle- versus procedure-based approach to educational innovation, supported by new knowledge media. Thirty-nine Knowledge Building initiatives, each focused on a curriculum theme and facilitated by nine teachers over eight years, were analyzed using measures of student discourse in a Knowledge Building environment-Knowledge Forum. Results were analyzed from the perspective of student, teacher, and principal engagement to identify conditions for Knowledge Building as a school-wide innovation. Analyses of student discourse showed interactive and complementary contributions to a community knowledge space, conceptual content of growing scope and depth, and collective responsibility for knowledge advancement. Analyses of teacher and principal engagement showed supportive conditions such as shared vision and trust in student competencies to the point of enabling transfer of agency for knowledge advancement to students; ever-deepening understanding of Knowledge Building principles; knowledge emergent through collective responsibility; a coherent systems perspective; teacher professional Knowledge Building communities; and leadership supportive of innovation at all levels. More substantial advances for students were related to years of teachers' experience in this progressive knowledge-advancing enterprise. (Contains 4 tables and 5 figures.)