Abstract This study analyzes an attempt at integration of a pre-school class, a leisure-time center and an elementary school in Sweden. The integration was organized in the form of Vertical Track which implies a successive development of groups comprising children between six and twelve years old, pre-school teachers, recreation pedagogues, and schoolteachers. The integration was prompted by state governed reforms such as the 1992 law allowing six-year olds to start compulsory school. The study is based on cultural-historical activity theory and was carried out as participant observation and action research. The study addresses the question of the potentials and alternative goals for change and development of the present school pedagogy and classroom practice that integration implies. Special attention has been paid to what tools might potentially mediate in processes of integration. A research and educational program, the 5thD, was jointly created between researchers and teachers and located in a Vertical Track. The capacity of this complex tool as a mediator in the multicultural Vertical Track structure was explored. It is argued that the Vertical Track as an instantiation of the integration reform represents an arena for potential expansive transformation. However, in order for integration to have an impact on the pedagogical practice in schools, teacher interactions need to be mediated by communicative and conceptual tools. It is suggested that the 5thD program is an example of such tools. Keywords: Integration, pre-school teacher, recreation pedagogue, schoolteacher, contradiction, expansive learning, mediation, and tool.