In this chapter, we trace the movement – over the course of the 2010–2020 decade – of interventions developed within the Wits Maths Connect-Primary project (WMC-P), and the scaling-up of the project from ten schools to provincial and national contexts. The focus of key interventions, the rationales for them, and the ways in which this approach to expanding scale differs from the larger-scale policy interventions are discussed. Learning outcome data, usually in a pre-/post-test design model, from all the interventions in the WMC-P project are included. We discuss this evidence of impact, and reflect on what the outcomes suggest as critical areas for focus in the next decade. In-service capacity-building through work with subject advisors and pre-service primary teacher education form particularly important thrusts within the emphases going forward.