This study examined, through an action research case study approach, the extent to which teachers at Newbury Charter School used data to inform their instruction. The study focused on the following questions:1. How are the instructional decisions and actions of administrators and teachers informed by data?2. What barriers and enablers influence the use of data?3. What processes can a leadership action research (AR) team identify, and engage in to support teachers use of data for informing instructional decisions?An action research (AR) team, composed of school administrators, gathered information about teachers data use, the supports and challenges they faced, and the leadership actions which supported and promoted data use for informing instruction. The process followed a single iterative cycle during which the AR team sought information, examined findings, clarified understanding of the issue, and planned and implementing action steps to support teachers use of data to inform their instruction. Data collected on teachers access to and use of student data indicated that they used various data sources, to include data from state and district assessments, as well as other informal sources they believed to be valuable. Informalsources included teacher created assessments and student work product. Teachers reported using data for multiple purposes but placed more emphasis on using them to group students, to determine what students knew, and to identify what should be taught or retaught. Utilizing a participatory action research approach, the study explored the experiences of the AR team as it collaborated and engaged with teachers to examine how data were used to inform instruction.