The purpose of this study was to further address the "for whom" in the question of the effectiveness of modified schema-based instruction (MSBI) to teach mathematical problem solving to students with intellectual and developmental disability by evaluating whether positive outcomes from prior research would be replicated with elementary students in a different context. We aimed to analyze the "under what conditions" variable and assess feasibility of teacher-implemented MSBI in a small group. This study evaluated the effect of teacher-implemented MSBI in a small-group setting on level of independence in and maintenance of mathematical problem solving for elementary students with extensive support needs in semi-rural Australia. Implications for future research and practice are discussed.