Behaviourism proposes successful learning to be dependent on the performance of conditioned behaviours that are distinctly observable and objectively measurable. Over the past 100 years, various behaviourist concepts have been superseded by sociocultural and cognitive learning theories, but the entwined areas of assessment in mathematics education have not received the same focus. Outdated beliefs and unquestioned norms surrounding behaviourist assessment ideologies continue to dominate schools' decision-making around mathematics education. This paper includes the theoretical foundations for a PhD that aims to surface the tension of what is said to be valued in mathematics as "success" and what is systematically labelled as "success".