<p>Does the exposure of children to immigrant peers with proficient language skills increase foreign language acquisition? We examine this in the context of Norway, where all students are taught and assessed in English from the beginning of compulsory school. We use this, combined with recent increases in immigration, to investigate the effect of exposure to English-speaking peers on the English language skills of Norwegian children. Exposure increases these skills, has no effect on other educational attainment, and does not appear to reflect general peer quality effects or other confounding factors. The effects are evident only within same-gender peers and for children with initially above-average English proficiency. This suggests important roles for social interaction and baseline language competencies.</p>