The policy question analysed in this project was how the incentives of public decision-makers may impede the implementation of admissions rules that are both fair and efficient, reduce social segregation and improve learning outcomes. The project had two work packages: The first one addressed the question of how the incentives of public decision makers may impede the implementation of fair and efficient admission rules. The second work package leveraged our datasets in order to identify marginal students, based on preferences estimated under work package one. Focusing on these marginal students, which are students that just by chance ended up in one particular school and peer environment, enabled us to estimate causal effects of the learning environment on learning outcomes. The findings were used to assess the effects of assignment policies on learning and diversity to deepen our understanding of the importance and wider effects of admission rules and deliver concrete policy recommendations. In cooperation with other Leibniz Institutes, universities and government agencies, the project contributed to establishing a network for admissions practices and their consequences for learning outcomes.