Language is one of the most remarkable developmental accomplishments of childhood and a tool for life. Over the course of childhood and adolescence, language and literacy develop in dynamic complementarity, shaped by children’s developmental circumstances. Children’s developmental circumstances include characteristics of the child, their parents, family, communities and schools, and the social and cultural contexts in which they grow up. This chapter uses data collected in Growing up in Australia: The Longitudinal Study of Australian Children (LSAC) that was linked to Australia’s National Assessment of Literacy and Numeracy (NAPLAN) to quantify the effects of multiple risk factors on children’s language and literacy development. Latent class analysis and growth curve modelling are used to identify children’s developmental circumstances (i.e. risk profiles) and quantify the effects of different clusters of risk factors on children’s receptive vocabulary growth and reading achievement from age 4 to 15. The developmental circumstances that gave rise to stark inequalities in language and literacy comprise distinct clustering of sociodemographic, cognitive and non-cognitive risk factors. The results point to the need for cross-cutting social, health and education policies and coordinated multi-agency interventions efforts to address social determinants and break the cycle of developmental disadvantage.