On the basis of examples concerning the grouping of students in lower secondary education, the paper explores four topics that have consequences in terms of equity and fairness in education : the first is linked with the relative weight of the regulatory constraints and of the room of manoeuvre of actors in the operation of the system; the latter may obviously present some positive aspects, but they may also lead to the fact that students may be treated very differently according to the school in which they are enrolled; the second analyzes the process by which some students are selected for specific treatments; here the observation is that the selection may carry large inconsistencies leading interrogation in terms of fairness of the process; the third is linked with the fact that the context of schooling is partly manufactured (for example that a student is schooled with peers that are majoritarily high or low achievers) may lead to relatiuvely wide disparities in learning outcomes; last, the issue of a possible conflict of interest between the system as a whole and that of its actors (teachers, parents) is discussed.