According to the American School Counselor Association, school counseling interns' competence should be measured by an instrument grounded in professional standards. However, no valid and reliable instrument exists to assess school counseling interns' competencies. We created and validated a school counseling supervision instrument with four subscales: Foundational Skills and Dispositions, Multicultural Considerations and Student Services, General Education and Special Education Process, and Classroom Management and Collaboration/Consultation. We provide implications for interns, site supervisors, and university supervisors/faculty.