This study employs whole-brain modeling by coupling structural and functional connectivity to investigate hierarchical reorganization in intrinsic and extrinsic brain processing during childhood. Using data from the Adolescent Brain Cognitive Development (ABCD) study, we integrate diffusion and functional MRI to characterise how structural architecture supports functional dynamics in young children. We aim to uncover how hierarchical organisation relates to behavioural variability in relation to mental illness. This research provides critical insights into the neural mechanisms underlying typical development and offers a framework for understanding deviations associated with behavioral and developmental challenges.