When solving basic number fact problems (e.g., 4x5=20), students with mathematical learning disabilities (MLDs) make qualitatively different kinds of errors than both typically achieving and low-achieving students. This study explores the origin of these qualitative differences through a detailed analysis of one student with an MLD. Data were…

Within the Response-to-Intervention framework, students who fail to profit from high-quality general education instruction, accommodations, and supplemental instruction progress to a more intensive intervention program, sometimes referred to as "Tier III." This article describes a problem-solving approach to designing such intensive, data-based,…