This article discusses a 2-year action research project carried out in Catalonia using a sample of seven schools with varying degrees of social and ethnic diversity, focusing on the debate and critical perspectives surrounding the question of family-school relationships. It underlines four considerations, which are seen as symbolic, practical and probable barriers to this partnership: unequal power relationships, diversity and inequality of families, the grammar of schooling and how teachers view their professional identity. We present an action research project that involved the critical participation of the teaching staff in these seven schools and designed to answer the following question: under what conditions could family-school relationships be improved with and for all families, pupils and teachers? The conclusion discusses both the limitations of the critical action research and the lessons learnt from it: (a) the true transformation of the grammar of schooling is a slow and complex process; (b) this process is positive for teachers and makes their work better and easier; (c) the evaluation of constructive critical support is relevant and highly valued; and (d) the assessment of improved daily actions is key to making them visible and sustaining the change process.