The present research aims at describing and gaining knowledge about the lexical availability in Spanish in a sample of students of the Basque Country, categorized according to the model of bilingual education they have attended. The Basque Autonomous Community (henceforth BAC) establishes a frame of two official languages: Basque and Spanish. In order to fulfill this legal precept, one of the tasks of the public authorities of the Basque Country is well-defined: to assure the general knowledge of both languages, adopting the appropriate measures for such a purpose. The fact of both languages being co-official makes it necessary to analyze the situation of bilingual education from the moment it was established. This will reveal whether the bilingual school model the young population has attended influences the lexical variety in their speech production in Spanish; specifically, their production in social contexts. The measuring method used here is based on the common model for measuring lexical availability, that is, the words that first come to mind are the ones that are most available.