Personalizing Psychosocial Intervention for Children With Disruptive Behaviour

Inclusion Criteria * Diagnosis of Oppositional Defiant Disorder (ODD), Conduct Disorder (CD) or Attention Deficit Hyperactivity Disorder (ADHD) determined by the supervising Clinical Psychologist based on DSM-5 diagnostic criteria on the C-DISC; and/or clinically at risk symptoms on the Child Behavior Checklist/Teacher Report Form (t score \> 60) * Clinically severe impairment in social, family, peer functioning demonstrated by the parent- and teacher-completed Impairment Rating Scale (IRS) or the virtually administered Columbia Impairment Scale (CIS) * No evidence of Autism Spectrum Disorder (based on parent and teacher report) or Intellectual Disability (based on the Kaufman Brief Intelligence Task-II OR school reports or psychoeducational assessments). Exclusion Criteria * Presence of Autism or Intellectual Disability * Evidence of cognitive delays or an intellectual disability (based on the Kaufman Brief Intelligence Test-2 (KBIT-2), verbal and/or IQ composite standard score below 80 or collateral information) * Child behaviour or emotional functioning that make group participation not possible * Child preference for individual treatment. * Parent behaviour or emotional functioning that make group participation not possible * Parent preference for individual treatment.