Implementation of the No Child Left Behind (NCLB) legislation has been accompanied by demand for data systems capable of providing a longitudinal record of each student's educational experiences and performance over time. The national Study of Education Data Systems and Decision Making is examining both the implementation of student data systems per se and the broader set of practices involving the use of data to improve instruction, regardless of whether or not the data are stored in and accessed through an electronic system. The conceptual framework developed for the study identifies six prerequisites and supports for data-informed decision making: (1) state, district and school data systems; (2) leadership for educational improvement and the use of data; (3) tools for generating actionable data; (4) social structures and time set aside for analyzing and interpreting data; (5) professional development and technical support for data interpretation; and (6) tools for acting on data. This interim report draws on case study findings from the first round of site visits in nine purposively sampled districts, nominated on the basis of the strength of their data use activities, and on data from secondary sources. The report describes the student data systems available to school staff members, how school staff members are using the systems and other forms of student data, teachers' understanding of data displays and data interpretation issues, and the supports and challenges for school-level use of student data in planning and implementing instruction. Reflections of the case study informants and the pattern of activity across their districts and schools with different practices suggest a number of guidelines for schools and districts embarking on the implementation of data-informed decision making: (1) Districts are finding that providing school-level data coaches is an important support for school-level use of data to inform instruction; (2) A common curriculum and curriculum-aligned benchmark assessments increase the likelihood that school staff members will make extensive use of a district's data system; (3) If teacher use of data is the goal, then it is desirable to have curriculum and instruction staff members involved in the initiative; (4) Teacher buy-in for the data system and its use should be sought early and maintained continuously; (5) Professional development should include training on how to interpret data and how to translate data into changes in instructional practice; (6) District policies should be examined to identify and remove policies and procedures that undermine teachers' use of data to inform instruction; and (7) School leaders need to build teachers' mutual trust to a point where teachers are comfortable working with colleagues to examine data that reflect on their teaching performance. Three appendixes include: (1) Case Study and Survey Data Sources; (2) Scenario, Exhibits, Items, Rubrics, Item Score Distribution and Mean Score; and (3) Scenario Development and Reliability Information. (Contains 32 footnotes, 8 figures, and 21 exhibits.)