This article focuses on multilingual primary-aged children and their families in a post-industrial city in England. Such pupils, sometimes identified in education policy as "underachieving," often have rich experiences of learning that are hidden from their mainstream teachers and unrecognised in national assessment regimes. The article draws on the concept of "funds of knowledge" and cultural-historical activity theory (CHAT) to reveal the complex and continual interplay of the global and the local in the lives of the children and their families, and expose the tensions between the policy goals in education of promoting "diversity" and "inclusion". Findings from longitudinal case studies, using linguistic ethnography methodology, track the experiences of the pupils in home, community and mainstream and complementary schools, showing the range of their learning experiences across languages and cultures. They reveal the potential contributions of their home and community learning experiences to their success in the mainstream. This has important implications for policy and practice related to multilingualism in education in England. To understand the constructions of "official" underachievement of children such as those in the study, we need to understand how they experience directly in their lives the outcomes of confused and sometimes contradictory education policies. (Contains 2 figures, 1 table, and 2 notes.)