NECESSARY CONDITIONS: Understanding patterns and variations in math course-taking among high school seniors to increase completion of four years of math Abstract This mixed methods study explores high school seniors’ math course-taking decisions and what changes school leaders can take to increase the percentages of students taking four years of math in high school. Through an analysis of district-level administrative data and a survey completed by seniors at a high performing, diverse high school in Northern California, this study illuminates many reasons for why these patterns and inequalities occur. Findings reveal institutional, classroom and individual factors that impact students’ decision-making around taking math senior year. Keywords: secondary math course-taking, seniors, high school math pathways, equity in math