Sargisson, Rebecca J.Powell, Gina2026-03-202026-03-202025https://hdl.handle.net/10289/18139Background: Externalising disorders (EDs) are among the most common behavioural problems in childhood, with disruptive behaviours in Aotearoa New Zealand schools recently identified as a major concern. Despite widespread implementation of interventions, uncertainty remains about their effectiveness and alignment with developmental theory. Objectives: This systematic review aimed to evaluate the effectiveness of interventions for primary-aged children (5–14 years) exhibiting EDs, assess the certainty of evidence, examine moderating factors of intervention outcomes, and consider implications for practice in the Aotearoa context. Methods: Following PRISMA 2020 guidelines, eight databases and trial registries were searched. Eligible studies were randomised controlled trials (RCTs) of interventions targeting EDs in primary-aged children. Risk of bias was assessed using the Cochrane RoB 2.0 tool, and findings were synthesised narratively given heterogeneity across interventions and outcomes. Results: Twenty-three RCTs met inclusion criteria, yielding 148 outcome measures. The majority (77.7%) were at high risk of bias, largely due to reliance on unblinded raters, insufficient reporting, and baseline imbalances. Sensitivity analyses excluding very low-certainty studies left only 17 outcomes, of which eight were rated as high certainty. Behavioural outcomes were heavily over-represented (67.5%), with relational and environmental outcomes underexplored. Moderator analyses indicated that interventions targeting single subgroups produced more favourable outcomes than multisystem approaches, though overall evidence quality limited confidence in these findings. Conclusions: Current RCT evidence for ED interventions in primary-aged children is of low quality, restricting firm conclusions about effectiveness. The imbalance in outcome domains and mechanisms suggests an overemphasis on behaviourist approaches at the expense of relational and ecological factors. High-quality, large-scale RCTs are urgently needed, particularly those addressing classroom environments, relational mechanisms, and culturally grounded approaches relevant to Aotearoa. Registration: The protocol for this review was registered with the Open Science Framework (OSF). https://osf.io/9afzx/enAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.Thesis