Using data to inform classroom decision-making is a salient facet of teachers' professional practice. However, some evidence suggests that teacher data use practices are unevenly distributed within and across school contexts. In response, the present study examined school-level (elementary, middle, and high) differences in four categories of data use practices among public school teachers (N = 303) from at least 68 schools and 52 districts in Illinois, USA. Concomitantly investigated were differences in data use practices by school locale (city, town, suburban, rural), school socioeconomic status, teacher experience, and teacher primary position. Multiple regression analyses revealed school-level differences for two categories of data use practices, namely using data for ordinary classroom instructional decision making, and using data for programmatic instructional decision making. In both cases, elementary teachers were more likely to use data than middle and high school teachers. Some data use practices also varied as a function school locale, teacher experience, and teacher primary position. Implications for practitioners, researchers, and future directions are discussed.