This essay presents the analysis of the school dimensioning which has been realized through the vertical organization choice of “Istituto Comprensivo of the school ”Mommsen” in Rome. The objective of this reflection is to consider risks and chances laid ahead by dimensioning. Our intention is to observe the experience of Mommsen school, to recognize improvements in strategy. The essay is articulated as follow. We start showing the “scenarios change” and normative references. Then, we present the procedure which trought the “IC Mommsen”school has faced this change to promote a general critical reflection. In fact, our goal is to replay to some important problems as the continuity, the closeness of local authorities or the “new” school organization.