Tackling early leaving from education and training (ELET) is one of the headline targets for education policy in the European Union. Although ELET rates have been decreasing in most member states, male, socially disadvantaged and immigrant students remain overrepresented in ELET figures. Moreover, students in vocational tracks and students who experienced grade retention are steadily more at risk of ELET. These risk factors are, however, considered mostly beyond the reach of individual schools and educators. This study therefore targets to pinpoint more alterable factors that can support at-risk students' educational resilience. As there is broad scientific consensus to consider ELET as a potential endpoint of a gradual process of disengagement from school, this study explores the added value of the self-system model of motivational development (SSMMD) in explaining behavioural school (dis-)engagement among students considered at risk of ELET based on their sociodemographic and educational background characteristics. We make use of survey data purposefully collecting data from 483 students across 25 inner-city vocational secondary schools in Flanders. The structural equation modelling (SEM) testing the hypothesised structural relations of the SSMMD, overall showed empirical support for the model being an interesting theoretical framework for explaining student (dis)engagement through perceived social support and self-processes. The SEM, however, also showed few relations contradicting the theoretical hypotheses. We discuss how the hierarchically tracked and segregated educational context in Flemish urban vocational schools could provide explanations for these findings.