This chapter summarizes a set of research studies that focus on high school course offerings, takings, and effects. Improving high school experiences and having students graduate from high school ready for college are national priorities under President Obama's Race to the Top initiative. Doing so by expanding access to advanced courses dates back a decade to President George W. Bush and the National Governors Association's efforts in the No Child Left Behind era. Courses are still seen as the gateway to higher student performance and access to college. From research done in collaboration with Dylan Conger and Mark Long, we found that taking more rigorous math courses increases students' likelihood of being ready for college math, and that gaps in math course taking explain about one third of the gap between White and Black students and White and Hispanic students' readiness for college. Advanced courses do matter--even taking just one advanced course improves students' test scores, likelihood of graduating from high school, and likelihood of attending a four-year university. Schools, however, could do more to overcome the gap. We found that the best predictor of schools' offering advanced courses was their having a critical mass of students with very high prior achievement. Resources, however, were not a factor.