The development of the modern nation-state was an inherently centralising process. Education policy and the institutionalisation of mass public schooling played a key role in this process, facilitating industrialisation and the generation of mass loyalty toward the state. In almost all federal systems, however, education policy remained an exclusive jurisdiction of the sub-federal level, with important long-term implications. Adopting a most dissimilar case design by using two contrasting cases -- Canada and Germany -- this paper argues that boundary control has been an effective mechanism for sub-federal governments to consolidate and retain authority over education policy, despite recurring pressures for more harmonisation or even uniformity. Although both federations differ profoundly in terms of their institutional characteristics and macro-sociological contexts, boundary control strategies variously allowed sub-federal actors in both federations to thwart efforts of the federal level to assume a greater role in education policy over time.