Purpose: The purpose of this study is to describe the variability of principals' classroom observations across schools and to relate classroom observations to the schools' instructional climate. This helps identify the conditions under which classroom observations effectively improve instruction in some schools and not in other schools. Design/methodology/approach: Data for the study are from surveys from principals (n=319) and teachers (n=15,818) matched to administrative data on principals and schools. Data are analyzed using factor analysis, latent class analysis, and regression. Findings: There is no evidence that the frequency, duration, or instructional focus of classroom observations varies across schools with different student demographic characteristics or student performance levels. There is also no evidence that the frequency or duration of conducting classroom observations relates to the instructional climate of the school. However, there is evidence that conducting observations with a focus on instructional improvement relates to the instructional climate of the school after controlling for school and principal characteristics. These findings suggest variability in the implementation of classroom observations. Originality/value: The paper provides useful information to guide the preparation and support of principals in order to use classroom observations most effectively for improving instructional opportunities. (Contains 6 tables.)