This paper explores the relationship between socio-economic status, ability grouping and children’s educational outcomes. The study takes the form of a systematic review to examine available evidence-based articles which are selected by following a specific set of inclusion criteria. Articles are then analysed in terms of the research questions which look to examine the relationship between children’s socio-economic background and ability group placement, and the impact of ability grouping on the learning (cognitive and behavioural) of children from low socio-economic households. The review suggests that children from lower socio-economic status backgrounds are more likely to be placed in lower ability groups, sets or streams. This placing is proven to have an overall negative impact on behaviour, as well as failing to close the achievement gap as children in lower groups make slower cognitive progress than children in other groups. Furthermore the general consensus arising from the literature is that ability grouping does not have the positive evidence base to support its use in primary classrooms. Especially when concerning the learning of children from lower socio-economic status backgrounds.