Current state and federal reform initiatives rely heavily on the ability of multiple stakeholders to access and use information from statewide longitudinal data systems (SLDSs) to improve student achievement. State policymakers have indicated through reform plans that states are best positioned to achieve this goal by developing and implementing various policies affecting educators. They will also, for the first time on a larger and more visible scale, use student achievement as a primary indicator of educator and program effectiveness. Therefore, policymakers must understand the importance of defining the purposes for and developing the policies to support a valid and reliable teacher/student data link. This policy brief outlines some of the most critical challenges facing states and districts as they develop and implement policies based on the teacher/student data link and provides guidance on the emerging best practices for effective implementation, including: (1) States must first determine how the data from the teacher/student data link will be used, which should drive the policy conversation around how the state will define teacher of record; (2) Although IT and data staff are critical in developing the technical solution to capture the appropriate data, policymakers and educators must own the process from the beginning because they are best positioned to resolve issues relating to the appropriate attribution of student learning to educators; (3) Teachers must have the means to periodically review their rosters to ensure that they are linked to the correct students; and (4) States and districts must work together collaboratively on all aspects of the teacher/student data link. (Contains 5 resources.)