This chapter presents the ambitious vision of the Barcelona Summit Agreement, which aspires for all Europeans to be able to speak two languages in addition to their mother tongue. It details how English-speaking countries in particular, and non-English-speaking countries more generally, are experiencing great difficulty fostering plurilingual citizens. The chapter sets the stage for the rest of the book, which aims to answer an overarching question: Can an education system realise the aim of the Barcelona Summit Agreement? The chapter presents Ireland as a microcosm of sorts of other English-speaking countries as much of what applies to Ireland in terms of developing a plurilingual population will be applicable to other countries. The benefits of realising the ambition of the Barcelona Summit Agreement are delineated. The argument is made that the most opportune period to develop plurilingual citizens is childhood and adolescence, and the ideal location to achieve this goal is in primary and post-primary schools. Readers are informed that the goal of realising a plurilingual populace through an education system is not a hypothetical endeavour; the European Schools system is presented as an example of an education system that meets, if not exceeds, the vision of the Barcelona Summit Agreement. Cross-age teaching and other novel strategies that could be employed to foster plurilingual students through the education system are introduced. The empirical research that was undertaken in Ireland with modern foreign language students, teachers, school leaders, parents, and other stakeholders as well as in Brussels with members of the senior management of the European Schools system is outlined.