In the last years, the population in Catalonia has increased in nearly a million people due to the arrival of immigrants from outside Spain. This new situation has created a challenge for the educational system and the acquisition and use of Catalan in schools. In order to ensure that Catalan continued to be the main language in schools, the Catalan government initiated a program whose main objectives are social cohesion and providing support for the acquisition of Catalan for students who incorporate late to the educational system. The so-called aules d’acollida are classes where Catalan for academic and conversational purposes is taught to those students who do not have enough knowledge of Catalan to be in a regular class. This paper provides results on the acquisition of Catalan by the students who attended the aules d’acollida in year 2005-06. All students attending aules d’acollida in primary and secondary schools in Catalonia took two tests that evaluated the acquisition of Catalan and school integration/adaptation. The results show that a) students achieved better results in comprehension skills than in production skills, b) the fewer hours the students spent in the aules the higher the proficiency they achieved, and c) students who had a Romance language as their L1 obtained better results than student who spoke non-Romance languages.