PROJECT SUMMARY/ABSTRACT Academic tracking is a widely used practice that groups students into classes according to prior academic performance, but has been criticized as a form of structural racism and discrimination, as it leads to the concentration of Black and Latinx students in low-performing tracks. In addition to potential long-term impacts on education attainment, a powerful social determinant of health, academic tracking may directly affect adolescent social networks and substance use behaviors. By grouping students together with similarly performing peers, tracking may reinforce school disengagement and risky health behaviors like substance use, violence, and delinquency among lower-performing students. However, no known studies examine the health implications of academic tracking nor tested whether interventions to dismantle tracking positively impact health. Advancement via Individual Determination (AVID) is a successful college preparatory program that works in part by “de-tracking” students. AVID targets students from groups under-represented in higher education, like Black and Latinx students, places them in rigorous college-preparatory courses, and provides academic and social support to ensure their success. In our pilot study, a handful of students within 5 public schools were randomized to AVID. We found the program led to connections with more pro-social peers and lower odds of substance use and delinquency. When applied school-wide, AVID trains schools to ensure all students have access to rigorous college-preparatory courses. However, there are no studies testing the health effects of AVID's school-wide program. We propose a longitudinal study of adolescents attending 5 AVID schools and 10 matched comparison schools (matched on location and student demographics) from racially and ethnically diverse communities in Southern California. Participants will be followed for 4 years to test whether exposure to AVID leads to a) lower rates of 30-day substance use (primary outcome--defined as any alcohol, tobacco, vaping, cannabis, prescription, or illicit drug use in the prior 30 days), and other substance use behaviors, violence and delinquency; b) increased enrollment in college-preparatory course taking and healthier social networks (measured by fewer peers engaged in substance use, more peers engaged in school, and more school-related adults); and c) whether associations between AVID and substance use are explained by reduced racial/ethnic disparities in college-preparatory course taking and healthier social networks. We will follow 3,570 9th-12th grade students at intervention and control schools for 4 years, collecting administrative education data and health behavior and social network survey data as they progress through high school and transition to college and/or the work force. This study will yield critical knowledge that can inform education and health policy regarding academic tracking and the use of de-tracking interve...