This article discusses policies that support professional development in an era of educational reform. It highlights the importance of understanding how teachers acquire and use new knowledge and skills, and how effective professional development models can be designed to involve teachers as active and reflective participants in the change process. The authors examine key design principles that guide policy-makers and school reformers in promoting learner-centered professional development. These include the role of teachers as both learners and teachers, new designs for professional development, school culture and critical inquiry, elements of effective curriculum frameworks, and lessons learned for educational policy regarding teacher professional development. The article emphasizes that the nature and specific type of teaching and learning that reformers understand is key to teacher professional development. This is the main obstacle to achieving systemic reform. The authors suggest guidelines for this article, including the need for teachers to reflect on their practice, construct new roles in the classroom, and adopt new teaching methods. They also stress that the success of this reform depends on teachers being able to learn new skills and attitudes while unlearning old teaching practices and changing their expectations of students. The article also discusses the need for professional development to include concrete teaching tasks, inquiry, reflection, collaboration, and a focus on student work. It highlights the importance of sustained, intensive, and collaborative professional development that supports teachers in developing new knowledge and skills. The authors argue that traditional models of teacher training are insufficient and that new approaches are needed to support teacher professional development as a lifelong process. The article also discusses the need for new institutional structures and agreements to support teacher professional development. These include professional development schools (EDPs) that provide opportunities for teachers to learn through collaboration, observation, and reflection. The authors argue that EDPs are essential for preparing future teachers and supporting the development of new teaching practices. The article also discusses the need for new structures and opportunities outside the school, such as professional communities, school-university collaborations, and partnerships with youth organizations. These structures provide opportunities for teachers to engage in collaborative learning and professional development. The article also discusses the need for policies that support learning communities outside the school, including professional associations, evaluation committees, and systems dedicated to educational innovation. These policies must be flexible and responsive to the needs of teachers and the profession. The article concludes that effective professional development requires a shift from traditional models of teacher training to more collaborative and reflective approaches. It emphasizes the importance of creating a supportive environment for teachers to learn and grow, and the need for policies that promote lifelong learning and professional development for teachers.This article discusses policies that support professional development in an era of educational reform. It highlights the importance of understanding how teachers acquire and use new knowledge and skills, and how effective professional development models can be designed to involve teachers as active and reflective participants in the change process. The authors examine key design principles that guide policy-makers and school reformers in promoting learner-centered professional development. These include the role of teachers as both learners and teachers, new designs for professional development, school culture and critical inquiry, elements of effective curriculum frameworks, and lessons learned for educational policy regarding teacher professional development. The article emphasizes that the nature and specific type of teaching and learning that reformers understand is key to teacher professional development. This is the main obstacle to achieving systemic reform. The authors suggest guidelines for this article, including the need for teachers to reflect on their practice, construct new roles in the classroom, and adopt new teaching methods. They also stress that the success of this reform depends on teachers being able to learn new skills and attitudes while unlearning old teaching practices and changing their expectations of students. The article also discusses the need for professional development to include concrete teaching tasks, inquiry, reflection, collaboration, and a focus on student work. It highlights the importance of sustained, intensive, and collaborative professional development that supports teachers in developing new knowledge and skills. The authors argue that traditional models of teacher training are insufficient and that new approaches are needed to support teacher professional development as a lifelong process. The article also discusses the need for new institutional structures and agreements to support teacher professional development. These include professional development schools (EDPs) that provide opportunities for teachers to learn through collaboration, observation, and reflection. The authors argue that EDPs are essential for preparing future teachers and supporting the development of new teaching practices. The article also discusses the need for new structures and opportunities outside the school, such as professional communities, school-university collaborations, and partnerships with youth organizations. These structures provide opportunities for teachers to engage in collaborative learning and professional development. The article also discusses the need for policies that support learning communities outside the school, including professional associations, evaluation committees, and systems dedicated to educational innovation. These policies must be flexible and responsive to the needs of teachers and the profession. The article concludes that effective professional development requires a shift from traditional models of teacher training to more collaborative and reflective approaches. It emphasizes the importance of creating a supportive environment for teachers to learn and grow, and the need for policies that promote lifelong learning and professional development for teachers.