Languages of Catalonia
The main cause of Spanish and Catalan social bilingualism in modern Catalonia was large-scale migration from the rest of Spain during the 20th century, as Catalonia started a significant industrialization which demanded an increased workforce from elsewhere. Spanish has historically been spoken among a minority of civil servants born in other regions in Spain and among segments of the wealthiest bourgeoisie. Spanish has also been spoken as a second language by most Catalans, as it has been the only official language over long periods since the eighteenth century.
Bilingual education
In addition to Castilian Spanish being the primary official language of Spain, the kingdom also has several co-official regional languages which enjoy equal and unbiased constitutional protection and promotion: Catalan/Valencian (in Catalonia, Valencia and the Balearic Islands), Galician (in Galicia), Basque (in the Basque Country and the northern zone of Navarre) and Aranese (in Val d'Aran, Catalonia).