The present study aims to critically review global experiences of school curriculum based on student voice and agency and analyze participation and negotiation models in selected educational systems. Despite extensive theoretical emphasis on the importance of student voice and agency, evidence indicates that student participation in many educational contexts is reduced to limited and symbolic opportunities. This gap constitutes the central problem of the research. The research method is a critical review with an analytical-interpretive approach, conducted through targeted searching in reputable databases and analysis of 77 scientific sources. The findings were organized into four main areas: the conceptual link between student voice and agency with emphasis on the mediating role of agentic engagement; curriculum structures in selected educational systems (Ireland, New Zealand, Estonia, South Korea, and Finland); participation and negotiation models including the Lundy model, Boomer's approach, and the Negotiated Integrated Curriculum; and the challenges of realizing agency at structural, cultural, and institutional levels. The results indicate that realizing authentic agency requires simultaneous changes in curriculum flexibility, revising assessment systems, modifying attitudes toward student capacity and teacher roles, and creating participatory school cultures. Furthermore, in centralized educational systems like Iran, realizing such transformations is accompanied by greater challenges. The findings can provide a basis for rethinking curriculum policies and practices in Iran.