Research and policy reports estimate that 10%-40% of U.S. children and adolescents currently have or very recently have had at least one significant mental health condition. Students who exhibit substantial behavior and emotional problems in school often show less severe problems when younger. Screening for less severe problems at younger ages can help educators direct extra support to students who may be likely to benefit. The present study explored the diagnostic validity of a brief teacher-rated behavior screening procedure for a national sample of 957 elementary school students--just over 12% of whom were school-identified with Emotional Disturbance (ED) and had an active Individualized Education Program (IEP). Diagnostic classification analyses were used to compare screening outcomes with IEP data for each student. Results indicated that the screening procedure correctly identified children with ED in over 90% of cases with classification accuracy being higher for younger students and female students. Study limitations, directions for future research, and practical implications about using this screening procedure are also discussed.