In this dissertation, I investigate several questions of interest in the fields of economics of education and economics of teams. In the first chapter, based on initial work with Laurent Rossignol, we focus on tracking in education. We provide evidence of tracking gaps in the French education system: tracking does not solely depend on academic performance but also on gender and socio-economic status. Our main contribution is to disentangle the impact of differences in students' aspirations from the impact of teachers' grading and track recommendations on these tracking gaps. The second chapter, joint with Antoine Chapsal, aims at understanding some of the incentives and psychological effects associated to teamwork, based on team squash da...