Policy shapes practice, and the increasingly important realm of professional development is no exception. In order to identify effective professional development policies and strategies, a Stanford University research team examined the policy frameworks supporting high levels of professional development activity in four states. The states--Colorado, Missouri, New Jersey, and Vermont--were selected as "professionally active" based on evidence of high levels of teacher participation in professional development in the 2008 Schools and Staffing Survey (SASS), administered by the National Center for Education Statistics, and the teacher surveys associated with the 2009 National Assessment of Educational Progress (NAEP); a reputation in the literature for enacting reforms that are consistent with the research base on "effective" professional development; and improvements in student achievement as measured in the 2009 NAEP. Students in all four states scored above national averages on the NAEP. Teachers in all four states had high participation rates in a wide range of professional development, from teacher induction to curriculum support and study groups focused on specific subject areas. While their approaches to professional development vary, the four states share a number of key characteristics and face similar challenges, which are outlined in this policy brief. All have professional development standards, induction and mentoring programs for beginning teachers, and a state-level organization or professional board that oversees teacher licensing, professional teaching standards, and professional development. Most also require professional development plans for teachers and minimum levels of professional development for license renewal. All provide a range of supports and incentives for professional learning. The authors found that state policies and systems that ensure accountability and monitor professional development are critical factors in implementing effective professional development across a variety of local districts, schools, and contexts. But to ensure the quality of that professional development, it is equally critical to couple state efforts with professional associations and intermediary organizations that help extend the reach of state agencies, offer learning supports of many kinds, and provide a voice for local stakeholders and outside experts. [For the full report, "Teacher Professional Learning in the United States: Case Studies of State Policies and Strategies. Technical Report," see ED515891.]