Through comparative case study, we seek to understand the ways in which actors in high schools use and think about performance data. In particular, we compare data use in higher and lower value-added schools. Data use is conceptualized here as having access to a host of available performance data on students, using them to guide instructional decisions, and building cultures in which data are seen as vehicles for improvements in practice. While our findings do not show consistent differences in the higher and lower value-added schools, they do allow us to set out an expanded conceptualization of school data use.