In this paper, we share features of the Mental Starters Assessment Project (MSAP) teaching and assessment materials from South Africa that integrate early algebraic approaches in an initiative focused on early arithmetic. The features of generalized arithmetic described in the early algebra literature that are incorporated into the MSAP materials are detailed: attention to number relations/properties and base ten structure, pattern, and moves between key representations. The mechanisms through which these features are integrated are: inclusion of open number sentences with a focus on equivalence, verbalisations of equivalence, attention to patterns in calculations in base ten structure, and key representations and their interconnections. The trajectory of outcomes from iterative scaling-up trials suggests that integration of algebraic features alongside arithmetical goals builds mental mathematical skills in ways that are grounded in a relational sense of number.