Policymakers across the nation are leading efforts to ensure that every classroom has an effective teacher. Faced with the need to dramatically improve student outcomes, states have embraced a policy agenda that promotes and supports teacher quality in many ways, including developing evaluation and compensation policies, targeting professional development, determining the characteristics of effective teachers through research, and identifying effective teacher preparation programs. It is incumbent upon state policymakers to invest time and resources into not only developing a shared vision for addressing teacher quality but also understanding the implications for state data systems to ensure the successful implementation of these policies. Without this proactive, deliberate approach, policymakers will find their plans constrained or undermined by data systems that do not meet policy needs. State policymakers must prioritize these five actions to ensure that their state has the necessary data capacity and processes to inform and support state teacher effectiveness policies: (1) Collect and link key data on students and teachers at the state level; (2) Implement the policies and practices necessary to support a high-quality teacher-student data link; (3) Provide educators with timely access to data; (4) Ensure that educators receive training on data use to improve student achievement; and (5) Implement state policies to ensure that teacher preparation programs use data to improve their programs and train teacher candidates to use data. A checklist and a list of resources are included.