Introduction: The development of immigrant students' language proficiency is one of the main challenges facing education professionals today. Our study was a longitudinal analysis of Catalan and Spanish language acquisition. Method: Participants were 72 immigrant students (27 Spanish speakers and 45 non-Spanish speakers) enrolled in compulsory secondary education in Catalonia (Spain). Two different instruments were applied: a sociolinguistic questionnaire and a parallel psycholinguistic test in Catalan and Spanish language. Results: Results indicate that the socioeducational context favors acquisition of both languages, and furthermore, it tends to equalize knowledge of these languages. Similarly, the home language variable lost its importance, as significant differences between Spanish- and non-Spanish speakers were not found. Conclusions: Beyond the connotations of language proficiency in the school context, these results may be an indication of this group's progressive adaptation to the host society. Furthermore, the results from Spanish- and non-Spanish speakers suggest that the Catalan context may diminish the initial significance of immigrant students' home language.