Recent scholarship has examined how accelerated math trajectories leading to calculus take shape during middle school. The focus of this study is on advanced math course taking during the critical yet understudied period that follows: the transition to high school. Data from the High School Longitudinal Study of 2009 are used to examine advanced math course taking in ninth grade, including both track persistence among students who took advanced math in middle school and upward mobility among students who took standard math in middle school. Results reveal sizable racial gaps in the likelihood of staying on (and getting on) the accelerated math track, neither of which are fully explained by prior academic performance factors. Interactions with parents and teachers positively predict advanced math course taking. In some cases, interactions with teachers may also reduce inequality in track persistence, whereas interactions with counselors increase such inequality. Implications for research and policy are discussed.