In just the last ten years, goaded by broad and still unsettled cultural shifts, education practices have changed dramatically. Schools are no longer just recording and analyzing inputs--dollars spent, number of days of instruction, numbers of students per teacher--but pushing their data-gathering and analysis efforts into the brave new world of outcomes. Today's educators are deciphering, and using, the results of student assessments better than ever. And it is not a reform at the margins. The "New York Times", confirming the scope of the trend, recently reported that nearly all states are building high-tech student data systems to collect, categorize and crunch the endless gigabytes of attendance logs, test scores and other information collected in public schools. In this article, the author takes a closer look at three schools that have integrated data into their instructional decision making. She examines a traditional public school, a district-turned-charter school run by an education management organization, and a relatively new charter school. The experiences of these schools illustrate the benefits of mining both internal assessments and standardized test results for data to guide curriculum decisions and inform classroom instruction. (Contains 1 figure.)