Research on the international secondary students (ISS) is scarce compared with the proliferating literature on their tertiary counterparts. This paper focuses on social integration experiences of ISS from diverse ethnic backgrounds, the undergirding macro-, meso-, and micro-mechanisms, and the supports needed for their successful integration. It draws on a subset of data from a longitudinal qualitative study through an interdisciplinary conceptual framework. This study employs multiple case study designs with critical intercultural hermeneutics as an interpretive approach. Research methods involve (a) serial interviews with six ISS that spanned the 2022-2023 school year; (b) in-depth interviews with their parents, homestays, teachers, and agents; (c) online observations of the students' virtual communities; (d) documents; and (e) research journals. It uncovers three mechanisms undergirding ISS' social integration challenges: lack of ethnic proximity, a departmentalised classroom system and capital defence. This study suggests that stakeholders and researchers of ISS must obviate deficit-oriented and assimilationist perspectives, which attribute social integration challenges solely to ISS' limited knowledge of mainstream culture and language. Instead, a paradigm shift is necessary to redefine the criteria for successful social integration as harmonious interaction with students from diverse ethno-cultural backgrounds, encompassing both culturally dominant and minority groups, with educators playing a central role in fostering this integration.