Algebra I is considered a "gatekeeper course" as it is required for students to gain access to higher-level coursework. 80% of K-12 students are eligible to take Algebra I in eighth grade, yet only 24% of eighth graders actually take the course. Black students are even less likely than their peers to be enrolled in Algebra I in the eighth grade, which ultimately impacts their math options in high school. The purpose of this critical race mixed-methods (CRMM) study is to demonstrate how tracking policies and inequitable access to high-quality and culturally relevant math teachers, and curriculum act as mechanisms that push Black students out of the STEM pipeline by influencing their options before they even make it to high school. In this convergent critical mixed methods study (QUAN + QUAL) the researcher collected and analyzed qualitative interviews with 21 Black high school students and three years of student transcript data for 1,561 Black seniors in one K-12 public school district in southern California. Ultimately, this project seeks to determine which variables contribute to the likelihood that a Black student is enrolled in a course "Beyond IM3" by their senior year of high school. My hope is that this study will help researchers understand the limited racial diversity in STEM fields, while also situating math as one of the major deterrents of Black students' interest and persistence in STEM. This research could be impactful for developing systems of multilevel support for Black students in STEM classrooms and could serve as an impetus for changes in math curriculum, policy, and teaching practices. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]