Family language practices (FLP) are interlaced with families’ language biographies. Consequently, children’s exposure and language experience are prone to variation. A growing body of literature shows the impact of amount of language input on the development of bilingual children’s receptive and expressive vocabularies (Cohen & Mazur-Palandre 2018; Hoff et al. 2014; Thordardottir 2011). This paper explores oral language in both languages of 21 typically developing bilingual French/English first grade children (mean age: 6;4) who attend a French/English dual language programme at a public school in France. The children, who differ in the amount of exposure they have had to each language, come from one of three home language backgrounds – English-dominant; French-dominant; or English and French. We explore the effects of language exposure on several measures of lexical richness. Parent questionnaires provide information on three independent variables related to FLP: current exposure, cumulative exposure from birth, and home literacy exposure (parent-child shared reading). Data in French and English are collected using standardised receptive vocabulary tests (EVIP, Dunn et al. 1993; BPVS, Dunn et al. 1987) and a story generation task to explore expressive vocabulary (Frog, where are you? Mayer 1969). The narratives are coded in the CHAT format of CHILDES to assess several measures of lexical richness: Malvern’s D (Malvern et al. 2004); number of different verbs; number of different nouns; and number of different adjectives. Correlations are calculated between the language exposure measures and the lexical diversity scores. Initial results suggest that children’s lexical richness strongly relates to cumulative exposure as well as home literacy exposure, independently from the family’s home language background. Finally, through the presentation of three case studies, each representative of the different family backgrounds, we explore how FLPs may impact dual language maintenance in a monolingual society.