The relevance of this study follows from the distinction between formal admission to higher education and students' actual ability to use university resources and participate effectively in academic and social life. The article aims to develop an integrative model explaining how inclusion is converted into equal social opportunities and how this process can be evaluated in Kazakhstan's higher education institutions. A critical integrative literature review and theory-building synthesis were conducted. The analytical corpus comprises 72 scholarly and policy sources published between 1989 and 2026, with most sources dating from 2021 onward. Evidence was synthesised through rights-based, capability, redistribution-recognition-representation, social model of disability, intersectionality, and belonging lenses. The synthesis yielded a five-link logic of inclusion: rights and resources; conversion conditions; resource use; participation, agency, and belonging; and equitable educational outcomes. The main original contribution is the concept of an "access-participation gap", which separates indicators of formal accessibility from those of effective participation, together with a multilevel matrix for evaluating this gap. The model indicates that universal design for learning complements but does not replace individual reasonable accommodations, while student voice and disaggregated monitoring create an institutional feedback loop. Practically, the model can support audits of university policy, teaching, digital environments, support services, and educational outcomes. The review does not estimate causal effects; it offers a transparent conceptual framework and testable propositions for subsequent empirical research.