Across OECD countries, individuals without tertiary-educated parents tend to be considerably under-represented among entrants to tertiary education. However, inequalities tend to accumulate throughout an individual's educational career. In particular, the period from starting upper secondary to entering tertiary education is critical in determining students' future career and education choices. Understanding how socio-economic disparities at earlier levels may influence entry rates to tertiary education will be essential if policy makers are to design better policies to improve equity.