The Company You Keep:

Peers are considered important for adolescents’ educational achievement and attainment, though little conclusive evidence demonstrates peer effects on these outcomes. This dissertation shows that it is not only important where you go to school, but also with whom you go to school.
The dissertation consists of four related but self-contained papers on the effects of peers and friends on educational outcomes, such as educational choice, achievement and performance.
The research presented in this dissertation, shows that even in a socially and economically equal society such as the Danish, there are still tendencies for unequal outcomes in education.
The dissertation's focus is whether and how student compositions affect these inequalities. Using quasi-experimental methods and longitudinal data on social networks, the dissertation contributes to a deeper understanding of peer effects and thus the causal relationships between student compositions, learning outcomes and educational decisions.
Overall, the dissertation shows that the effects of peers are highly heterogeneous, meaning that the individual student is not affected equally by all of the students within his or her peer group.
The dissertation further shows, that although the Danish educational system is formally un-tracked, the students are informally segregated based on their preferences of friends and achievement, leading to unequal outcomes of educational achievement and attainment.