In response to the vast amounts of data associated with the accountability movement and the rhetoric of data-informed decision-making, we interviewed 16 principals to find out what streams of data they used and what decisions they made by using the data. We found that: (a) student achievement data are predominantly used to the extent of neglecting other streams of data such as student and community background data and school process data; (b) student achievement data are used more for accountability purposes--for assessing "of" rather than "for" the learning; (c) different streams of data are rarely used together to derive rich meaning for decision-making; and (d) school districts differ in the extent to which their principals use data to improve curriculum and instruction. The study pointed both to the challenges and to the opportunities of making data-informed decisions to improve our schools. (Contains 5 tables.)