Despite growing recognition of the education crisis in South Sudan's displacement settings, empirical evidence on the specific barriers facing children within individual internally displaced persons (IDP) camps remains scarce. This study examined the structural, socio-economic, and protection-related factors limiting school enrolment, attendance, and retention among internally displaced children in Mangalla IDP Camp, Central Equatoria State, South Sudan. A sequential explanatory mixed-methods design was employed: a structured survey administered to a stratified random sample of 151 participants (parents, teachers, humanitarian workers, and school administrators) selected using Yamane's formula, followed by 30 purposively selected key informant interviews. Quantitative data were analysed using descriptive statistics, while qualitative data were subjected to inductive thematic analysis. Findings reveal that 79.5 percent of respondents consider education only partially accessible, and economic hardship was identified as the single most significant barrier by 72.2 percent of participants. Infrastructure deficits, teacher shortages, safety risks, and the complete absence of secondary schooling compound educational exclusion. Drawing on the Right to Education Framework and Bronfenbrenner's Ecological Systems Theory, the study demonstrates how these barriers interact and reinforce one another across ecological levels. The study contributes localised, camp-level empirical evidence addressing a gap in the education-in-emergencies literature and offers actionable, context-specific recommendations for humanitarian organisations, government authorities, and community stakeholders, including the urgent establishment of secondary schools, household economic support programmes, and integrated psychosocial services.