Educational processes are cumulative by nature, i.e. earlier phases in education structure the realm of options available to educational processes in later life as well as the long-term employment and life opportunities. Therefore, (a) early inequality can lead to large inequalities regarding education and participation later on, (b) inequality can persist across the lifespan, and (c) inequalities in education can affect all other areas of life, generating further inequalities there. Research into the emergence of social inequalities in the acquisition of education and its assessment thus need to consider educational processes and educational institutions across life. Moreover, individual educational processes are influenced by a wide range of factors which cannot be adequately addressed and taken into perspective by one isolated discipline. In this respect, research calls for an interdisciplinary collaboration of researchers from different disciplines (for example from educational science, economy, psychology, sociology but also political science or philosophy regarding educational policy or normative issues).