In a two-sided coalitional matching problem agents on each side of the market simultaneously form coalitions which then are matched to coalitions from the other market side. We assume that each agent has preferences over groups on his own market side and over groups on the opposite market side....

We consider the problem of how societies should be partitioned into classes if individuals express their views about who should be put with whom in the same class. A non-bossy social aggregator depends only on those cells of the individual partitions the society members classify themselves in....