Inequality in access to quality education is wide-ranging across and within countries. This study examines determinants for adolescents’ school enrolment in private and public schools in Bissau, Guinea-Bissau, including 2,039 randomly selected school-attending adolescents. The survey methodology was built on the Planet Youth collaboration and is the first of its kind in the setting. The critical determinant for attending a private school rather than a public one reflects parental socioeconomic background, i.e., education, employment status, and financial resources, not gender. Overage class enrolment is common, particularly in public schools and among boys rather than girls. National and international collective action and innovative education policies are needed for Bissau-Guinean adolescents to enjoy their right to the quality education they are entitled to.