College education becomes increasingly important for individuals' career prospect. However, many students enter college academically unprepared (Jackson & Kurlaender, 2014). As a response, high school curriculum is tasked as the gatekeeper of students' academic proficiency that equips students with essential knowledge and skills for postsecondary education (Attewell & Domina, 2008). It is necessary to understand the step-by-step progress students make in every academic year (AY) and their academic pathways across high school, and to identify factors shaping these coursework pathways that lead to postsecondary attendance. This study analyzed a random sample of students enrolled in Texas public high schools as first-time ninth graders in 2004 and who also stayed on track throughout high school were targeted (n = 21,141; 5.5% of the target population). The findings demonstrated the complexity and fluidity of students' coursework patterns and pathways, the critical role of students' academic performance in math in altering students' course-completion trajectories longitudinal, and the importance of staying on track of high school curriculum since freshman to ensure later academic achievement and college attendance. Practitioners should consider the necessity of tracing students' academic progress in all subjects longitudinally, especially for math and the role of computer science (CS) courses.