The Structural Extension Spine: Modelling the emergence of algebraic reasoning in early mathematics

Background: The transition from arithmetic to algebra remains a persistent challenge in early mathematics education. While structural awareness is widely recognised as foundational to this shift, the developmental mechanism through which learners come to operate on mathematical structure remains insufficiently theorised. Aim: This article advances the Structural Extension Spine as a theoretically derived model explaining how recursive numerical activity is progressively reorganised into structurally generalised reasoning, thereby accounting for the emergence of early algebra prior to formal symbolism. Setting: Six Grade 2 teachers in public schools participated in a series of three workshops foregrounding the use of structure in the teaching of patterns. Methods: Adopting a theory-generative interpretive orientation, the study emerged through disciplined analytic engagement with classroom practice within a Foundation Phase professional learning initiative in South Africa. Document analysis of curriculum materials, workshop activity and classroom observations functioned as theoretically generative sites revealing persistent tensions between recursive participation and structurally oriented reasoning. Results: The analysis renders visible a developmental reorganisation in which mathematical activity shifts from succession to relation to generality. Conclusion: The resulting six-phase Structural Extension Spine models the progressive availability of structure as an object of thought, culminating in reasoning capable of sustaining algebraic generalisation. Contribution: By theorising how learners come to operate on invariant relationships, the Structural Extension Spine offers a principled developmental account of algebraic emergence and repositions structure as the primary object of mathematical reasoning.