Step 1: Understanding the Concept:
The question asks to classify "modelling" within the major schools of psychotherapy. Modelling is a therapeutic technique where a client learns new behaviors by observing and imitating a model (either the therapist or another person).
Step 2: Detailed Explanation:
Modelling is a core concept of Albert Bandura's Social Learning Theory, which is a cornerstone of behaviorism and behavior therapy. The theory posits that learning can occur through observation, imitation, and modelling, without direct reinforcement. Because it focuses on observable behaviors and learning principles, it falls squarely under the umbrella of Behaviour Therapy.
(A) Psychodynamic therapy focuses on unconscious conflicts and insight.
(C) Humanistic-existential therapy emphasizes self-awareness, free will, and personal growth.
Neither of these approaches uses modelling as a primary technique.
Step 3: Final Answer:
Modelling is a technique rooted in learning theory and is therefore a type of Behaviour therapy.