Over the past few decades, market forces have characterized the evolution of Quebec’s education system. By giving parents the freedom to choose the school that their children attend and schools the opportunity to select their students, political leaders have opened the door to intra- and inter-school competition (Kamanzi, 2018, 2019). This results, among other things, in educational and social inequalities where students are separated according to their abilities and, implicitly, their social background (Desjardins, Lessard and Blais, 2011; Marcotte-Fournier, 2015; Marcotte-Fournier et al., 2016; Larose, 2016, Hurteau and Duclos, 2017). Using data from the Pisa 2015 survey, we study the effects of market practices on school cohesion. We analyze this phenomenon through the feelings of belonging, trust and cooperation among secondary school students. Our analyses show that school stratification and the presence of competition are linked to school cohesion. On the one hand, students in private schools are those who maintain a strong cohesion in their school environment. On the other hand, the more competition there is within the institution, the higher the sense of belonging. Based on these findings, the study suggests some possible interpretations to better understand the nature of competition, but also to consider ways to establish a healthy cohabitation between cohesion and the logic of school markets in the context of Quebec’s school system.