In this paper, we detail the outcomes of a small-scale intervention study that aimed to support the mathematising processes of Grade 2 South African learners when working with additive relations problems. We report on the mathematising shifts that were evident in pre- and post-test responses prior to and after a sequence of 13 intervention lessons. The intervention drew from Askew's "Big books of word problems" teaching resources, which were based on Realistic Mathematics Education and Cognitively Guided Instruction. The intervention involved intervention and control groups located within isiZulu speaking classes in one Johannesburg township school. The outcomes indicated greater shifts for the intervention group in their extent of awareness of structure and progression towards use of a more formal mathematics register. The results suggest the need for more focus on supporting learners with the setting up of models, and attunement to the association found between demarcating quantities within models and overall outcomes.