Disruptive behavior disorders (DBDs) constitute an umbrella term for a variety of childhood and adolescent disorders; in particular, they are characterized by persistent oppositionality, defiance, aggression, rule violation or dysregulated behavior. However, from the perspective of Educational Therapy, diagnostic classification alone is not a good explanation for why disruptive behavior occurs in learning environments. This narrative review looks at the nosology of disruptive behavior disorders from an educational therapist’s perspective: from the Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR) and/or the International Classification of Diseases, Eleventh Revision (ICD-11), to the neuroscience of attention-deficit/hyperactivity disorder (ADHD) and cognitive disengagement syndrome (CDS). In particular, the author is interested in behavioral phenotype and functional mechanisms. The oppositional defiant disorder (ODD) and conduct disorder (CD) are formal disruptive/dissocial disorders, while ADHD is a neurodevelopmental disorder that may cause disruptive behavior in children and adolescents. CDS, formerly called sluggish cognitive tempo (SCT; Barkley et al., 2022; Becker, 2025), is an emerging research-supported syndrome, and is not considered a DSM-5-TR or ICD-11 disorder. In this review, educational therapists should conceptualize disruptive behavior by considering executive functioning, academic demands, social expectations, and environmental conditions within the application of the Cognition-Conation-Affect-Sensation (CCAS) model. Differentiated educational assessment should then move from observed behavior to antecedents such as functional abilities, learning demands and consequences and be tailored to each student. In this paper, the author has adopted the Educational Therapy model in which differentiated nosology establishes the clinical context, functional assessment identifies learning processes and interventions are made to address the learner's adaptive, academic, behavioral and social skillsets.