Recognizing the educational and economic benefits of a college degree, education policymakers at the federal, state, and local levels have made college preparation a priority. There are many ways to measure college readiness, but one key component is rigorous high school coursework. California has not yet adopted a statewide college readiness requirement, but a growing number of school districts--including Los Angeles Unified, San Jose Unified, Oakland Unified, San Diego Unified, and San Francisco Unified--now require students to complete the rigorous coursework, called the "a-g courses," that are necessary for admission to the University of California (UC) and the California State University (CSU) system. In this report the authors look at participation and performance in rigorous high school courses among California high school students, both overall and across demographic and racial/ethnic groups. While enrollment in rigorous courses has been increasing, particularly among students who are traditionally underrepresented in higher education, a large majority of California high school students are not taking the courses that can prepare them for college. Forty-three percent of high school graduates in 2015 completed the a-g requirement, and 27 percent of high school graduates in 2013 passed an advanced placement (AP) exam. Participation in advanced math, biology, chemistry, and physics courses is also low. In particular, only 30 percent of high school juniors and seniors enrolled in Algebra II and smaller shares enrolled in chemistry (28%) and physics (10%). As they monitor the progress of public high schools in preparing students for college, state policymakers and districts need to focus on indicators such as a-g completion, benchmark course-taking, and end-of-course exam (EOC) results. They authors also recommend tracking performance across student groups to help schools and districts address gaps in achievement and provide educational resources to students who need them most.