The present study investigated the development of linguistic awareness in children exposed to the early learning of a second language in Grades 3-5 of primary school, i.e. between the ages of 8 and 10. The aim was to determine whether this bilingual experience enhanced the development of phonological awareness in beginning readers in a bilingual French-regional language school programme compared with a population of monolingual children receiving traditional education. More specifically, in light of research promoting the hypothesis of a "bilingual advantage", we set out to determine exactly how long children need to be exposed to a second language before bilingualism starts to influence the development of their phonological awareness. Tasks designed to assess phonological awareness were administered to more than a hundred children. Results suggest that children who have undergone a bilingual school programme display a more highly developed phonological awareness than their monolingual peers from age 9 onwards, i.e. in Grade 4. These results are discussed in the light of ongoing research on bilingualism, bilingual education and threshold theory.