This article is based on an exploratory study that examines factors which predict children's performance on the numeracy component of the Australian National Assessment Program--Literacy and Numeracy (NAPLAN). Utilizing an ecological theoretical model, this study examines child, home and school variables which may enable or constrain NAPLAN numeracy performance. Data are presented from a nationally-representative sample of 2450 children participating in the Longitudinal Study of Australian Children (LSAC). Twenty-four children, home and school variables are tested as predictors of performance on the Year 3 NAPLAN numeracy assessment. The analysis includes an investigation of bivariate relationships between the outcome variable and each of the predictor variables. Following this a series of linear regression models are used to analyse the relation between child, home and school-related variables and NAPLAN numeracy performance. The results support the ecological model and point to the importance of a supportive home--school relationship on children's numeracy performance.