<p>In Swedish upper-secondary vocational education and training, work-based learning (WBL) is a compulsory but relatively short component within a predominantly school-based system. Although often presented as a bridge between school and work, WBL is encountered under uneven conditions. This article examines how students experiencing difficulties in WBL participation describe support and marginalisation during WBL. The study draws on interviews with 26 students from ten Swedish upper-secondary schools across nine vocational programmes and analyses the material using reflexive thematic analysis. The findings suggest that students’ experiences were shaped by the interdependence of four analytically distinct dimensions: School preparation, supervisory support, task design, and broader workplace conditions. These dimensions were later conceptualised as forming a support chain. When they aligned, WBL was more often described as coherent and educationally meaningful. When several were weak, participation was more often experienced as fragile, uncertain, or difficult to sustain. The study contributes a heuristic model for understanding how pedagogical, relational, task-related, and structural dimensions of WBL interact in shaping participation. Empirically, it adds to research on WBL by foregrounding the perspectives of students experiencing difficulties in WBL participation. The article concludes that strengthening WBL requires attention not only to access to placements, but also to the coherence of the conditions under which participation becomes possible and sustainable.</p>