In recent years there has been a positive change in the perception about bilingualism reflected in the increasing number of citizens demanding bilingual education. In this way, bilingualism constitutes a key element of opportunities (Saks 2002: 43) for any member of society regardless of their economic situation (Garcia 2009: 11). For this reason, the number of students joining bilingual programmes is increasing but, do they work? do they produce positive results? This research aims to analyse the differences in the English level between 4th year secondary school students belonging to bilingual and non-bilingual programmes in the Spanish region of Castilla-La Mancha. With the obtained information in our analysis we can determine if the bilingual programmes increase the communicative competence in English language of the students immersed in them. In addition, we will establish a comparison between the results acquired in the bilingual programme of Castilla-La Mancha and other programmes developed in different autonomous communities.