The mission of the Department of Education's Professional Development Team was to examine the best available research and exemplary practices related to professional development, and to summarize the lessons learned from this knowledge base in the form of principles that might inform practitioners and policymakers across the country and guide the department's efforts in the area of professional development. As developed by the team, the mission of professional development is to prepare and support educators to help all students achieve to high standards of learning and development. The principles ensure that professional development: focuses on teachers as central to student learning and on individual, collegial, and organizational improvement; respects and nurtures the intellectual and leadership capacity of teachers, principals, and others in the school community and reflects best available research and practice in teaching, learning, and leadership; and enables teachers to develop further expertise in subject content, teaching strategies, uses of technologies, and other essential elements in teaching to high standards. (ND)