An experiment has been performed with the view to reveal which modes of organization of collective activity (in groups of 3 and 2 persons) are most efficient from the point of view of development of systemic operations in younger schoolchildren. Correspondingly four experimental situations have been designed differing in the type of distribution of functions in the common activity. It is shown that organization of the collective activity at the content-object level produces the desirable effect in 78 % of cases.