Although socioeconomic disadvantage is linked with academic underachievement, many children from low-income backgrounds perform well in school. Which modifiable factors predict this academic resilience? We examine between- and within-person predictors of one important academic metric - mathematics performance - across adolescence in 1715 (796 male, 919 female) youth living in poverty in Ireland, using data from three waves (9, 13, and 17/18 years) of the Growing Up in Ireland study. Using linear mixed models, math performance was worse when adolescents had more socioemotional and behavioural difficulties, more child-parent relationship conflict, parents had lower expectations of the adolescent's educational achievement, and when primary caregivers had less education. Adolescents who had better intellectual self-concept and attended a non-disadvantaged school had greater math performance. This research adds to the growing body of work suggesting academic resilience is dynamic and multisystemic; it provides potential targets at multiple levels to promote such resilience.