Gaps in advanced high school coursework by socioeconomic status and geography persist in the United States, even among students with the ability and access to succeed in them. Lack of information on course availability and inaccurate self-perceptions may contribute to these inequities. We report on a large-scale experiment designed to increase Advanced Placement (AP) participation among underrepresented minority students and students attending rural high schools. Students and parents assigned to treatment received personalized outreach via multiple communication channels about APs offered at their high school in which they demonstrated potential to succeed. Outreach increased the probability of AP Exam participation in subjects in which students demonstrated potential to succeed by 1.1 percentage points, a 2.5 percent increase over the control group rate. This, in turn, increased the probability that students scored 3 or higher on those AP Exams by 0.5 percentage points, a 1.4 percent increase over the control group rate. Intervention effects were concentrated among underrepresented minority students attending non-rural schools and relatively less academically prepared students. The findings indicate that personalized course recommendations can increase equity in advanced high school course participation; however, designing outreach campaigns at scale that engage students is a crucial challenge to their efficacy.