Although much literature highlights the importance of teacher expectations for students' academic success, a very small number of studies used large-scale data to examine school-level factors associated with group-level teacher expectations -- defined as expectations that teachers have for many students in their class or school, rather than for a specific student -- in the US context. Using contextual data provided by mathematics and science teachers participating in the High School Longitudinal Study of 2009, the current study addressed this issue with paying attention to the roles of principal support and professional learning community in group-level teacher expectations. We found that both principal support and professional learning community were positively associated with group-level teacher expectations, even after controlling for other variables. We also found that much of the relationship between principal support and group-level teacher expectations was explained by professional learning community. Theoretical and policy implications are discussed.