There is considerable literature debating the positive and negative effects of setting on the mathematical self-concept of pupils. From a practitioner’s perspective the research findings are thought provoking as Muijs and Reynolds (2011) suggest setting has the potential to harm pupil’s self-concept when they are placed in lower ability sets. Whilst Boaler (2013) identifies that setting harms the academic achievement of pupils in the low and average ‘ability’ sets and does not improve the achievement of the pupil’s in higher ability sets. Consideration of the alternative to setting led to this comparative research which investigated the effects of setting and mixed ability grouping on the mathematical self-perception and mathematical attainment of two year 4 classes. The overall findings suggest that an intervention of mixed ability grouping had no statistically significant effects on mathematical self-perception and mathematical attainment in comparison to setting. The qualitative data gave an insight into year four pupil’s perspectives of setting in comparison to mixed ability grouping. It found that different schools have different approaches to setting and that the approach to setting along with one’s ability set influences how they describe the environment of setting and mathematical ability. Furthermore the findings identified that there were difference in the language used by pupils’ to label and describe mathematical ability when experiencing setting in comparison to mixed ability grouping.