Each year, considerable resources are spent on professional development to build teacher knowledge and skills. Yet not much is known about its impact on student achievement. Research confirms that professional development can affect teacher practice, but research has yet to confirm if those changes in practice improve student learning. Unfortunately, recent studies indicate that most teachers do not believe the professional development they receive is helpful or relevant for improving classroom instruction. State policies have traditionally left professional development decisions to school districts, providers, and teachers. Although states require teachers to complete a certain amount of professional development for license renewal, they do not typically regulate the quality or the relevance of the professional development completed. State policies focus almost exclusively on the amount of time required and the types of opportunities that can be used for license renewal. States rarely require the collection of data that could help determine whether professional development improves student learning. To enhance the quality of professional development and help ensure the investments made in professional development improve student learning, governors can lead efforts to develop new models of professional development based on what limited research indicates would improve both the quality and impact of professional development. Specifically, states should: (1) Gather and use student achievement data to assess the effectiveness of professional development; (2) Use teacher evaluations and student learning data to create individualized professional development plans for teachers; (3) Establish research-based state standards to create a vision for high-quality professional development; and (4) Create an incentive-driven professional development initiative for teachers to acquire advanced skills. (Contains 27 endnotes.)