The authors explored the effects of teaching conceptual model-based problem-solving instruction on students' ability to solve problems in various situations. Participants were 3 4th-and 5th-grade students with or at risk for mathematics disabilities. The authors used an adapted multiple-probe across-participants design to assess the functional relation between the intervention and the students' problem-solving performance. The results indicate that the intervention improved students' performance on researcher-designed criterion tests and a norm-referenced standardized test (i.e., the problem-solving subtest of the KeyMath Revised Normative Update; A. J. Connolly, 1998). The authors discuss the results in the context of providing students with appropriate educational opportunities, including carefully designed instruction. (Contains 2 tables and 5 figures.)