With the advent of the No Child Left Behind Act (2002 ), all students, including students with significant cognitive disabilities, must be included in measures of large-scale educational assessment and accountability. This article addresses the application of the assessment triangle developed by the National Research Council (Pellegrino, Chudowsky, & Glaser, 2001). Specifically, the article focuses on the first vertex of the assessment triangle, that of cognition, to examine characteristics of students with significant cognitive disabilities in representing what they know.