This paper considers the determinants of student participation in Michigan's large inter-district open enrollment system, known as Schools of Choice (SoC). Employing a rich dataset from the Michigan Department of Education, we examine the population of public school students in resident and non-resident school districts between the 2005-06 and 2012-13 academic years. We find substantial evidence that historically disadvantaged students are those most likely to participate in Schools of Choice: African American students and low-income students are more likely than their peers in their resident districts to make an inter-district transfer; they are, however, also the most likely among other Schools of Choice participants to exit the program. In addition, students who are relatively low performing on the state's standardized exam--especially in mathematics--are most likely to both participate in Schools of Choice and, among participants, the most likely to exit. We conclude by noting that these patterns are similar to those found among the determinants of more general forms of student mobility. An appendix provides tabular data showing: (1) Descriptive statistics of students based on enrollment in Schools of Choice (2005-2012); (2) SoC Participation by Students Classified as SoC 2005-2013; (3) District Rates of Student Exit Under SoC; and (4) District Rates of Student Entry Under SoC.