School leaders are often drowning in data but are unsure which forms of data will help them create a portrait of student achievement that will motivate staff to look beyond simple trends and delve deeper into root causes. Teachers often wish for more guidance on the kinds of data analysis and teaching strategies that will help them move the needle in classroom instruction. The authors offer five key principles of data use that can guide leaders in promoting deeper inquiry around data in their schools and districts so all students have the opportunity to achieve at high levels. These principles include articulating your purpose and commitment to equity, emphasizing the importance of pausing and reflecting before you make decisions on the basis of the data, being careful when using data to differentiate instruction, focusing on student engagement, and using your professional judgment. A key lesson? Note the authors, "Focus on the principles of effective data use, and not just the practices. Centering on the goals of improving education for all students, promoting an inquiry mind-set, and supporting teacher professionalism will help leaders use data for long-term continual improvement."