What factors support linguistic minority children in developing and maintaining literacy in their heritage languages (HLs)? Very few quantitative studies have explored the role of sociocultural factors, especially in the development and maintenance of HL literacy. This paper addresses this gap by examining how the sociocultural context affects general and specific aspects of Japanese literacy among school-age children of Japanese heritage living in Sydney. Specifically, it investigates the effects of society, community, and school on literacy development through three contrasting analyses: (1) Bilinguals vs. Monolinguals to examine the effects of the wider society; (2) Community bilinguals vs. Individual bilinguals to investigate the effects of community contact; and (3) Contact monolinguals (attending a full-time Japanese school in Sydney) vs. Non-contact monolinguals (in Japan) to study the effects of school. Free-style writing and a written test were used as data for the statistical analyses which highlight the characteristics of Japanese HL learners' literacy, and the need for mainstream support and appropriate teaching materials/methods. The results indicate that while the wider sociocultural context contributes significantly to HL literacy maintenance, community also plays an important role, and formal schooling in Japanese has the potential to override negative influences from the wider sociocultural context. (Contains 6 notes, 12 tables, and 1 figure.)