Proficiency With Number Concepts and Operations: Replicating the Efficacy of a First-Grade Mathematics Intervention.

This article focuses on a conceptual replication study evaluating the efficacy of Fusion, a small-group, first-grade mathematics intervention designed for students with or at risk for mathematics difficulties (MD). Conducted in a new geographical region with 240 first-grade students randomized to either a 2:1 or 5:1 student–teacher ratio Fusion group or a business-as-usual control, the study found that Fusion participants made greater gains than controls on proximal and some distal mathematics outcomes, notably on the ProFusion assessment and the Test of Early Mathematics Ability–Third Edition (TEMA-3). Unlike the original study, no significant differences emerged between the 2:1 and 5:1 group sizes in student outcomes or in the quantity and quality of instructional interactions. The findings highlight the importance of contextual factors such as core mathematics curricula and suggest that systematic, explicit small-group interventions can support early mathematics proficiency, while underscoring the need for further research on optimal group sizes and instructional mechanisms in diverse educational settings.