National longitudinal datasets offer opportunities to explore sub-samples of immersion pupils. Here, the Growing Up in Ireland (GUI) dataset is used to examine a sample (n = 569) of 9-year-olds attending Irish immersion schools, comparing immersion pupils whose families speak at least some target language (Irish) at home (n = 264), with those from English-only homes (n = 305), as well as mainstream school pupils from English-only homes (n = 6,704). The groups are compared on SES, home literacy activities, academic achievement, and attitudes both to school and to Irish. Children in Irish immersion are more likely to be in higher SES households with more home literacy activities, and these advantages appear further amplified among households where some Irish is spoken. It was socioeconomic and home literacy variables which significantly predicted scores in English vocabulary and mathematics, rather than home language or school programme. In attitudes, while Irish immersion pupils were somewhat less likely to look forward to school than mainstream pupils, they had much more positive attitudes toward Irish than them.