Schools today are more data rich than ever, requiring staff members to develop their data literacy--that is, their knowledge of how to use assessment data with other types of data to identify areas of effectiveness and to target instructional improvement efforts. Administrators and teachers are expected to use combinations of data (diagnostic and standardized test data, state assessment data, and local assessment data) to close achievement gaps, address literacy, evaluate and demonstrate program effectiveness, and improve instruction. In addition, reforms aimed at establishing standards-based instruction, connecting learning tasks to real-world situations, personalizing learning, and responding to diversity require the systemic use of a wide array of data by various groups and individuals. Data warehousing technology allows schools to collect, store, and analyze data more effectively. This article discusses the three key components of effective data use--focusing essential questions that guide data analysis, data warehousing technology that supports extensive data disaggregation, and a data team and data coach that ensures that the data is available and put to use. Taken together, these components support a culture of inquiry, continuous improvement, accountability, and purposeful data-driven decision-making--cornerstones of efforts to ensure the success of all students. (Contains 1 figure.)