International audienceThe input factors that may cause variation in bilingual proficiency were investigated in 38 French-English bilinguals aged six to eight, of middle to high socio-economic status, attending an international state school in France. Data on children’s current and cumulative language exposure and family background were collected through questionnaires given to parents and children. Language proficiency was measured using the standardised French and English versions of the Peabody Picture Vocabulary Test and the Student Oral Language Observation Matrix, a rating scale of oral competence, completed by children’s French and English teachers.The results indicated significant correlations between the language proficiency measure...