States experiencing success in raising student achievement are likely to be taking two key policy steps: identifying teaching standards that articulate what teachers should know and be able to do at different points in their careers and using those standards to develop more thoughtful certification and licensing systems, more productive teacher education and induction programs, and more effective professional development. This report examines progress toward a standards-based system of teacher development; the relationship between teacher knowledge and student achievement; and how to get knowledge to teachers through teacher development (effective systems of recruitment, preparation, induction and professional development). It concludes that student success hinges on good teaching, and states must institute a comprehensive teacher development system based on broad agreement about what teachers need to know and be able to do at different stages of their careers. Piecemeal teacher development policies, not connected by a common vision, are roadblocks to teaching and learning. A cohesive, comprehensive approach aimed at aligning policies and incentives for recruitment, certification, preparation, induction, and professional development under the same set of standards is needed. A sidebar discusses what teachers need to know and do. (SM)