This book contributes new perspectives from the Global South on the ways in which linguistic and discursive boundaries shape inequalities in educational contexts, ranging from Amazonian missions to Mongolian universities. Through critical ethnographic and sociolinguistic analysis, the chapters explore how such boundaries contribute to the geopolitics of colonialism, capitalism and myriad, interwoven, forms of social life that structure both oppression and resistance. Boundaries are examined across time and space as relational constructs that mark the terms upon which admission to groups, institutions, territories, or practices are granted. The studies further present alternative educational approaches that demonstrate the potential for agency and transgression, highlighting moments of boundary crossing that disrupt existing linguistic ideologies, language policies and curriculum structures.