While the debate regarding bilingual benefits persists within the cognitive sciences, education research has documented various functions that heritage languages (HL) serve their speakers through bicultural adaptation. The present study adopted a mixed-methods approach to gauge HL proficiency and use, cultural participation and ethnic and mainstream identities, and to examine multiple perspectives on HL learning with complementary schooling (CS) among British Sikhs. Seventy-four 6- to 15-year-olds completed scales for perceived oral and literate abilities, language use across contexts, British and Sikh identifications, and participation in cultural activities. Children filled in open-ended items, while parents and teachers discussed in interviews and focus groups, their motivations for HL learning and CS experiences. The majority of children self-reported 'good' proficiency, which differed between generations as impacted by home use and was associated with cultural participation and Sikh identification. Most children referred to practical utility while most parents regarded culture retention as the dominant motivation for HL learning. Teachers discussed how teaching beyond the second generation and language shifts presented both challenges and opportunities. Still, all parties corroborated on the pertinence of HL maintenance as facilitated by CS through 'culture learning' towards a strong ethnic identity and bicultural adaptation.