This chapter examines the racialization of mathematics education within the context of US K-12 education. While it is widely acknowledged that mathematics education houses chronic disparities between groups of students from more- versus less-dominant racial, ethnic and linguistic groups, fewer stories are told about the role of mathematics education in creating and fueling these disparities. The grand narrative of Black failure and White success is told without regard to the realities of racism, which shape the experiences of both Black and White (and all students) in US society. We argue that the same way in which Whiteness affords those identified as White with "material and non-material" benefits, the experiences of those identified as Black are shaped by entrenched notions of racial hierarchy and inferiority. As a result, mathematics education is a profoundly racialized experience in students’ lives. Increasingly, the processes and structures that play a role in students’ racialized experiences have been under investigation in the field of mathematics. The argument we develop in this chapter is developed from this work and our experiences as mathematics education researchers. Here, we set out to illustrate how the process of racialization gets constructed from the ground up--in moments of classroom life, within the schools in which those classrooms are situated, and within the structures and systems which constitute those schools.