["Journal of Intellectual Disability Research, EarlyView. ", "\nABSTRACT\n\nBackground\nInternational debates on inclusive education often position reduced‐size or specialized classrooms as either supportive provision or potentially segregating placement. Student‐perspective evidence remains limited, particularly for upper secondary students with intellectual and other documented disabilities.\n\n\nMethods\nThis sequential explanatory mixed‐methods study examined associations between reduced‐size classroom (RSC) placement and academic and socio‐emotional outcomes among 153 upper secondary students with documented disabilities in Wuhan, China. Students were enrolled in RSCs of no more than eight students (n = 47) or mainstream classrooms with resource‐room support (n = 106). Structural equation modelling estimated direct and indirect associations involving social integration, teacher support and academic self‐efficacy, with prior special education experience treated as a key covariate. Semistructured interviews with nine RSC students explained and contextualized the quantitative patterns.\n\n\nResults\nAfter adjustment, RSC placement remained statistically associated with social integration, teacher support and academic self‐efficacy, although estimates were attenuated. Bootstrap estimates supported indirect associations with subjective well‐being through social integration and teacher support, and with academic achievement through teacher support and academic self‐efficacy. Interviews highlighted belonging, personalized instruction, teacher closeness, reduced anxiety and academic confidence, while showing that students valued support quality more than placement labels.\n\n\nConclusions\nReduced‐size placement was associated with more favourable student‐reported outcomes when students perceived stronger relational security, individualized instruction and teacher support. Because placement was nonrandom and the quantitative data were cross‐sectional, findings should be interpreted as associational rather than causal. The study shifts attention from a simple inclusion‐versus‐segregation binary toward placement quality and support processes that may be especially relevant for students with substantial support needs in upper secondary education.\n\n"]