Effective teacher professional development (PD) is crucial for improving student learning in the 21st century. This report reviews 35 methodologically rigorous studies to identify features of effective PD that lead to changes in teaching practices and student outcomes. The report identifies seven key elements of effective PD: content focus, active learning, collaboration, use of models and modeling, coaching and expert support, feedback and reflection, and sustained duration. Effective PD is content-focused, focusing on teaching strategies related to specific curriculum content. It incorporates active learning, where teachers engage in the same learning activities they design for students. Collaboration is essential, with teachers working together in job-embedded contexts. Models and modeling of effective practice help teachers understand best practices. Coaching and expert support provide individualized guidance. Feedback and reflection allow teachers to refine their practices. Sustained duration ensures that teachers have time to learn, practice, implement, and reflect on new strategies. The report highlights examples of effective PD programs, such as the Science Teachers Learning from Lesson Analysis (STeLLA) program and the Reading Apprenticeship model. These programs demonstrate the positive impact of effective PD on student achievement. The National Writing Project (NWP) is another example of a successful PD initiative that supports teacher learning and student learning through collaborative, job-embedded professional development. The report also discusses the importance of creating conditions for effective PD, including adequate resources, shared vision, time for implementation, alignment of policies, and functional school cultures. Policy implications include adopting standards for PD, evaluating and redesigning school schedules, conducting needs assessments, developing expert mentors, integrating PD into school improvement initiatives, providing technology-facilitated opportunities, and offering flexible funding. In conclusion, effective PD is essential for improving teaching and learning. It should be well-designed, implemented, and sustained to support teachers' professional growth and student achievement. The report emphasizes the need for a comprehensive system of teaching and learning that supports students in developing the knowledge, skills, and competencies needed to thrive in the 21st century.Effective teacher professional development (PD) is crucial for improving student learning in the 21st century. This report reviews 35 methodologically rigorous studies to identify features of effective PD that lead to changes in teaching practices and student outcomes. The report identifies seven key elements of effective PD: content focus, active learning, collaboration, use of models and modeling, coaching and expert support, feedback and reflection, and sustained duration. Effective PD is content-focused, focusing on teaching strategies related to specific curriculum content. It incorporates active learning, where teachers engage in the same learning activities they design for students. Collaboration is essential, with teachers working together in job-embedded contexts. Models and modeling of effective practice help teachers understand best practices. Coaching and expert support provide individualized guidance. Feedback and reflection allow teachers to refine their practices. Sustained duration ensures that teachers have time to learn, practice, implement, and reflect on new strategies. The report highlights examples of effective PD programs, such as the Science Teachers Learning from Lesson Analysis (STeLLA) program and the Reading Apprenticeship model. These programs demonstrate the positive impact of effective PD on student achievement. The National Writing Project (NWP) is another example of a successful PD initiative that supports teacher learning and student learning through collaborative, job-embedded professional development. The report also discusses the importance of creating conditions for effective PD, including adequate resources, shared vision, time for implementation, alignment of policies, and functional school cultures. Policy implications include adopting standards for PD, evaluating and redesigning school schedules, conducting needs assessments, developing expert mentors, integrating PD into school improvement initiatives, providing technology-facilitated opportunities, and offering flexible funding. In conclusion, effective PD is essential for improving teaching and learning. It should be well-designed, implemented, and sustained to support teachers' professional growth and student achievement. The report emphasizes the need for a comprehensive system of teaching and learning that supports students in developing the knowledge, skills, and competencies needed to thrive in the 21st century.