The Assessment of School Counseling Competencies (ASCC) is a measure designed to assess school counseling trainees' student learning outcomes in four domains: (a) school counseling program development; (b) academic, career, and social/emotional student services; (c) evaluation and assessment; and (d) professional dispositions and behaviors. The ASCC aligns with standards from the Council for Accreditation of Counseling and Related Educational Programs and the American School Counselor Association, supporting sound evaluation processes and continuous programmatic improvement. This article (a) reviews the developmental needs of school counselors in training and the importance of sound evaluation measures; (b) introduces the ASCC as a tool to promote the development of reflective, ethical, and effective school counseling professionals; and (c) offers implications of the ASCC for quality program evaluation and research.