This article explores the mobilization dynamics of a school-based minority language revitalization initiative in the French Basque Country, known as the Ikastola Movement. Bringing the study of language revitalization into dialogue with social movement theory, I discuss how the solidarity of Basque language activists was influenced by state-level structures of power. Focusing on an early phase of mobilization from 1975 to 1981, I consider how political opposition to the Ikastola Movement created a series of ideological and institutional struggles for activists. I then examine how these experiences of struggle strengthened the solidarity of activists in the long run. Ultimately, I argue that the discursive and organizational solidarities mobilized by activists were crucial in allowing them to realize important political gains during the 1980s to 1990s. By way of conclusion I suggest avenues for future research on school-based revitalization movements that draw attention to the horizontal and vertical dynamics of collective action.