This chapter uses data from the K cohort of Growing Up in Australia: The Longitudinal Study of Australian Children (LSAC) to examine the numeracy skills demonstrated by children at different ages, and whether levels of numeracy skills vary for children from different socio-demographic backgrounds. The socio-demographic groups examined in this chapter are categorised by: child gender; socio-economic characteristics including family socio-economic position (SEP) (lowest 25%, middle 50%, highest 25%); mother’s working hours including mothers not working (those unemployed, on maternity leave, and not in the labour force), working less than 35 hours per week, or working 35 hours or more per week; and family characteristics, including family type (two-parent family, lone-mother family); and number of siblings in the household (no siblings, one or two siblings, three or more siblings).