Objective: This systematic review synthesises international evidence on behavioural and programmatic factors leading to the success of child and youth school retention and completion in low -and middle-income countries (LMICs) to inform policy and social and behaviour change (SBC) interventions. Data sources: The study follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines with the proposal registered on the International Prospective Register of Systematic Reviews (PROSPERO) database. Search strategy: A systematic search was performed on PubMed, ERIC, Web of Science, ScienceDirect, and Google Scholar databases for articles published from Jan 2015 to July 2024. Study selection: Reviewers independently completed screening procedures and reviewed eligible publications focusing on LMIC policy frameworks, cultural, gender, socioeconomic, infrastructural, human resource and geographic factors impacting school drop-out and SBC interventions. Data synthesis: SBC was rarely mentioned in intervention approaches, despite SBC activities being identified in programs targeting out of school children (OOSC), including training and capacity building, identification of key influencers, and the development of purposive SBC interventions. Facilitators to improved engagement and student retention included teacher training and capacity building, the use of structured syllabus, and targeting of participants from the education supply and demand sides. Cash transfer programs generally demonstrated positive impacts on student retention and reduced drop-out, including nutrition incentives in and out of schools. Conclusion: Complementary multipronged and multilevel SBC approaches that create greater engagement and partnerships with parents, teachers and the communities they serve, are a likely to achieve the greatest traction in addressing challenges of OOSC. PROSPERO registration ID: (anonymized for review)