These countries face a double challenge: they must expand secondary education while also ensuring that students who complete compulsory education are at least able to read and understand texts, and to use numbers, at a level that enables them to further develop their potential and participate in knowledge-based societies. For instance, between 2003 and 2015, the population of 15-year-olds enrolled in grade 7 or above increased by almost 500 000 students in Brazil, by more than 375 000 students in Turkey and by more than 300 000 students in Mexico, reflecting the increasing capacity of these countries to retain young people in school. These improvements are also evident in improved coverage rates of the national populations of 15-year-olds (enrolled and not enrolled) in PISA samples. Countries showing positive coverage trends also include Costa Rica, Indonesia and Uruguay.