Basque ikastola schools teach through the medium of the Basque language. Additionally, its curriculum, organizational model and position in its social and cultural environment also differentiate it from the mainstream educational system in Spain.

The ikastola is a product of the Basque nationalist movement. As education was becoming a nation-building tool in all of Europe around 1900, Sabino Arana, the founder of Basque nationalism, elaborated his own type of nationalizing school. The aim was to arrest the Spanish assimilation process carried out in mainstream education by developing a Basque counterpart, which would not only teach through the Basque language but also transmit the type of national values then propounded by the Basque Nationalist Party (Partido Nacionalista Vasco, PNV). Loyalty to the Christian religion (an important aspect of the Basque self-image) and to traditional values occupied a prominent place in the curriculum of the first ikastolas, which developed and expanded throughout the 1920s and during the Second Republic of 1931-36, and which federated regionally into the Eusko Ikastola Batza.

During the Civil War and the Franco dictatorship, when all manifestations of Basque language or culture were severely repressed, the ikastolas practically disappeared; but they emerged in strength at the beginning of the 1960s, coinciding with the new nationalism represented by ETA. These new ikastolas share some features with their pre-war forerunners, but there are also substantial differences: they were now a symbol of cultural anti-Franco resistance; they ramified into all Basque lands (also in France) beyond their earlier catchment area of Guipúzcoa and Vizcaya; and they have adopted more progressive teaching methods and leftist values.