Bennett, C., & Harris, J. J. (1982). Suspensions and Expulsions of Male and Black Students: A Study of the Causes of Disproportionality. Urban Education, 16(4), 399-423.

Black students are suspended far more often than white students. The extent of disproportion depends largely upon school and staff characteristics.

Full article can be found here:

http://journals.sagepub.com/doi/abs/10.1177/004208598201600402