The present study investigated evidence of the construct validity of scores from the Scales for Assessing Emotional Disturbance Rating Scale (SAED-3 RS), which is designed to help identify emotional disturbance (ED) as defined by U.S. law and regulations. The purpose of this research was to evaluate the degree to which SAED-3 RS scores differed between students with school-identified ED, students with school-identified learning disabilities (LD), and students without disabilities. The sample consisted of 2,193 K-12 students from throughout the U.S. The findings supported three hypotheses related to evidence of construct validity: (1) students with ED would differ from students without disabilities on all five dimensions of the SAED-3 RS; (2) students with ED would differ from students with LD on all dimensions of the SAED-3 RS except for the Inability to Learn dimensions; and (3) students with LD would differ from students without disabilities on all five dimensions of the SAED-3 RS, but that these differences would be smaller than the differences between students with ED and students without disabilities. Implications for practice and directions for future research are also discussed.