Background/Context: Access to rigorous courses in high school is essential for college success (ACT, 2005), but low-income students and students of color take fewer demanding courses than their white and Asian counterparts (Cowan Pitre, 2014; Theokas & Saaris, 2013). The issue of inequitable access to more advanced courses requires a deeper dive into course prerequisites, policies, and other requirements. This paper presents early results from a statewide longitudinal mixed methods study of high school students' course trajectories and the supports that schools provide to enhance college-readiness. Purpose: This study examines potential inequities in access to rigorous high school curricula based on school locale, demographics, race. The specific research questions are: 1. According to district course catalogs, what course trajectories do high schools offer, and what prerequisites does each school have that limits access to those courses? and 2. According to students' individual transcript data, what are students' actual course trajectories in high school mathematics, and how does the prevalence of trajectories into more rigorous courses vary across race groups? Setting: All data for this study come from the state of Delaware. Population: This study includes all Delaware high schools and more than 8,000 high school students from the graduating class of 2020. Practice: This paper focuses on practices and policies related to course offerings in English language arts (ELA) and mathematics in high school grades, including contextual differences across schools as well as differences in prerequisites that may support or hinder equitable access to rigorous curricula within some schools. Research Design: This is an observational study. The design is intended to identify and quantify current inequities in policy and practices through descriptive statistics, inferential tests of subgroup comparisons, and data visualizations. Data Collection and Analysis: For the course catalog analyses under research question 1, we consolidated data gathered from course catalogs of high schools across the state, and we then used qualitative coding to categorize each course (based on course name and course description) into five categories of rigor (college prep, honors, Advanced Placement, Dual-Enrollment, and International Baccalaureate). We then created interactive course trajectory models in RStudio using the "collapsibleTree" package to visualize all the available ELA and mathematics course trajectories at each of the 42 schools (see Figure 1 for an example). For the analyses of student transcript data under research question 2, we classified course titles and course codes in transcript data for more than 8,000 students using individual-level data from Delaware's statewide longitudinal data system (SLDS). To identify the most common trajectories and examine the flow of individual students' mathematical trajectories over their four years of high school, we produced Sankey diagrams of math courses from 9th through 12th grades (see Figure 2 for an example) across all students and schools, for individual schools, and for subgroups of students by race. Findings/Results: Results from the course-sequence models and advanced-course-offering profiles confirm that high schools have varying practices, rules, and prerequisites regarding ELA and mathematics course enrollment. Some schools have policies clearly restrict access to advanced courses, while other schools have few if any restrictions. Fisher's exact test revealed that differences in enrollment restrictions were found to be unrelated to racial composition or to average SAT scores. However, Title I schools were less likely (p<0.001) to offer unrestricted access. Results from the student trajectory analyses reveal that (a) there are many transitions where students jump up or down in course rigor, especially in their junior and senior years, (b) transitions are more prevalent in Math than in ELA, and (c) non-white students are less likely to transition into AP, Dual-Enrollment, or IB courses. Conclusions: The results presented in this paper suggest that access to challenging curriculum may not be equitably distributed across schools and school districts, and may not be equitably distributed across subgroups of students within some schools. However, the school-level differences identified here appear to be unrelated to three key demographic factors (e.g., percent non-white, percent passing the SAT college-ready benchmark, school size). The factors that explain why different high schools in Delaware provide more or less opportunity to enroll in advanced courses are one focus of the next stages of this five year research project.