Empowering teachers to use data effectively as part of a process of instructional improvement calls for schools and districts to engage in systematic collection and analysis of evidence as part of an ongoing school improvement cycle. In research and practice, the author has identified four steps school leaders--supported by central office--must take in order to launch and implement this work effectively and sustain it over time to lead to improvement. Identify a clear instructional focus to which all teachers can align their work; lead a schoolwide improvement process that facilitates ongoing learning as part of a plan, do, study, act cycle; collect and analyze multiple types of evidence from teachers and students to enhance instruction; and build a strong team to lead the work of improvement in professional learning.