Schools are awash in data, and teachers are being asked to gather data in a myriad of high-tech and low-tech ways. But gathering is not analyzing, and without analysis there is little reason to gather the data in the first place. Teachers need data-collection systems that lend themselves to rapid analysis and action. This article presents several methods teachers can use to leverage formative assessment data in ways that transform instruction and learning. A video clip showing how a middle school math teacher uses a free app to gather and display student responses and guide discussion is included.