The overall aim of this paper is to explore how certain input factors relate to bilingual children’s performance in English and French. The participants of our study were 38 French- English bilingual children aged six to eight, of middle to high socio-economic status, attending an international school in France. Data on the children’s language experiences and family background were collected through questionnaires given to the parents and the children. Language proficiency was measured using the standardised French and English versions of the Peabody Picture Vocabulary Test. Having examined the strength of the relationship between overall language exposure estimates and the language proficiency measures in each language, we then turn our attention to the relationship between the children’s current language input and each of the language proficiency measures, followed by the children’s current language output and the language proficiency measures. Next we investigate the relationship between the child’s stronger language and a number of variables related to language use. These are: the language the child finds easier to speak and prefers speaking; the language the child finds easier to read in and prefers reading in; the child’s cultural allegiance; the language used with friends in the school playground; the language used with toys, and the language(s) the child would choose to use in his/her perfect school. We will present the results of this study and discuss the implications of our findings. Here we highlight the need to find ways of promoting the child’s weaker language, especially if it is the minority language which is available only in a restricted number of domains. We pay particular attention to the important role played by friends in the promotion of the children’s weaker language.