Evidence-based school counseling requires that practitioners and scholars utilize formal counseling theory. Theories that inform school counseling must cohere with the unique needs of students and school environments. Therefore, we propose that school counseling theories must include the following constituents: (a) qualities of students and school environments, (b) empirical and professional endorsements, (c) school counseling customs, and (c) methodological relevance. We describe the utility of these constituents through example using a school counseling-specific theory, the Advocating Student-within-Environment approach.