This study explores how structural, compositional, and cultural characteristics of the teacher workplace affect an individual teacher's trust in colleagues. In particular, we investigate whether a homogeneous staff culture facilitates trust among teachers. Multilevel analyses on data of 2,104 teachers across a representative sample of 84 secondary schools in Flanders (Belgium) reveal that collegial trust is fostered when teachers agree on the teachability of the students in school. A mesomediation model demonstrates that the presence of a less homogeneous teachability culture explains the lower levels of collegial trust in socioeconomically disadvantaged schools. Our findings suggest that school leaders should focus on developing similar and positive conceptions among their teachers about students' teachability, in order to build social capital within the teaching staff to benefit student learning. (Contains 3 tables.)