Sociological or historical surveys on French elites highlighted at many occasions that "grandes écoles" graduated are over-represented at the top of the socio-professional hierarchy. These surveys showed that social capital constituted by passing through an elite higher educational institution and the co-optation networks among graduates from the same institution is a key asset to reach these prestigious social positions. But little is know on the concrete activation conditions of such relational resources. Focusing on one "grandes écoles" graduates subgroup (the graduates from one of the Ecole Normale Supérieure), our presentation aims to better understand how social capital is activated. Based on in-depth interview analysis and alumni associations archives analysis, we try to shed a light on the activation conditions of such relational school-based resources in diverse professional contexts. On the one hand, we show that crossing the analysis of the legitimate definition of the social link among the graduates and the norms and representations that structure the professional groups reached by graduates is a key insight to understand the relational resources activation possibilities. On the other, we analyze how the struggle within the alumni group to fix the « good » way of define school-based relational resources frame the activation possibilities of such resources.