This study was carried out within the framework of a long-term action-research project in schools in Barcelona, Spain, in which a large concentration of pupils come from diverse ethnic backgrounds and are at risk of social exclusion. Specifically, the introduction of the "Fifth Dimension" (5D) model into these schools is analysed here. 5D is an action-research programme partnership between universities and schools that has been developed by an international network of researchers and is based on a collaborative learning model, supported by information and communication technologies and by the university students themselves. This study focuses on the changes produced in school practices and in the role of teachers. Over a 4-year period, qualitative data were elicited from four primary school using linguistic methods, field notes, interviews and focus group with educators involved in the process. Cultural Historical Activity Theory was used as a framework for analysis of the coded data. The findings highlight the key elements for the change: consistency in the mediating devices (proposed tools and activities), reorientation of classroom interactions into forms of collaboration, the changing roles of the teachers to include design, observation and help, and the development of inter-institutional partnerships based on permanent negotiation.