Black and minority ethnic teachers are significantly underrepresented in British schools. Despite increasing anxieties about Britain's 'diversity shortage' among teachers, recent studies on the experiences of Black teachers generally, and Black male teachers specifically, remain rather sparse. Drawing on in-depth interviews with 25 Black Caribbean and Black African male teachers with five or more years of experience in London schools, this article deploys Bourdieusian conceptions of organizational habitus to explore the ways in which the national 'diversity shortage' can lead to a local 'diversity trap' in state schools that limits the range of roles Black male teachers are encouraged to pursue in schools. Findings suggest that pressures for Black male teachers to serve in racialized roles as community liaisons, role models, and school-wide disciplinarians, particularly for ethno-racial minority students, have stymied the long-term progress of Black male teachers towards departmental and administrative leadership -- ranks at which the diversity shortage is even more acute.