In a context of activation, welfare agents resort to explicit and implicit forms of categorisation to identify more precisely the target groups that can be activated. In the capability perspective, such a categorisation should be flexible enough to promote the conversion of entitlements into real capacity to act. In this perspective, the definition of an open “informational basis of judgement” (i.e. the criteria used to delimitate people's entitlements and duties, to the exclusion of all other types of information) and its practical implementation are key features for assessing the potential and limits of welfare policies. Based on a Swiss case study of school-to-work transition, the paper shows that though formally open, the investigated programme results in strong selectivity among the participants and emphasises the factors that explain this paradoxical result.