Academic tracking is a common practice in American high schools. While its impact on the lives of teachers and students is well documented, few studies pay close attention to the criteria used to determine high school students' academic trajectories or how teachers select and apply these criteria. This review, which examines the types of criteria guiding high school teachers' course recommendation decisions, is organized into four parts. First, the literature search process is described and the terms tracking and ability grouping are defined. Second, the significance of course placement is addressed through an examination of the relationship between tracking and the opportunity gap. Third, research drawing attention to the meritocratic and non-meritocratic criteria guiding secondary teachers' course recommendation decisions is examined. The review concludes by offering recommendations for making school-based course placement policies and the criteria driving teachers' decisions more consistent and transparent.