The United States government has become increasingly focused on school climate, as recently evidenced by its inclusion as an accountability indicator in the "Every Student Succeeds Act". Yet, there remains considerable variability in both conceptualizing and measuring school climate. To better inform the research and practice related to school climate and its measurement, we leveraged item-response theory (IRT), a commonly used psychometric approach for the design of achievement assessments, to create a parsimonious measure of school climate that operates across varying individual characteristics. Students (n= 69,513) in 111 secondary schools completed a school climate assessment focused on three domains of climate (i.e., safety, engagement, environment), as defined by the U.S. Department of Education. Item and test characteristics were estimated using the 'mirt' package in R using unidimensional item response theory. Analyses revealed measurement difficulties that resulted in a greater ability to assess less favorable perspectives on school climate. Differential item functioning analyses indicated measurement differences based on student academic success. These findings support the development of a broad measure of school climate but also highlight the importance of work to ensure precision in measuring school climate, particularly when considering use as an accountability measure. [This paper was published in "Educational Measurement: Issues and Practice" v38 n4 2019.]