Educational aspiration is an essential motivational psychological force that can encourage vulnerable children to strive for academic success and overcome their vulnerable circumstances. Based on the developmental contextualism theory, this study utilized two waves of data from the China Education Panel Survey to construct a cross-lagged model and investigate the factors that influence the educational aspirations of vulnerable children. The study found that, first, early risk factors and school support had significant negative and positive effects, respectively, on vulnerable children's later educational aspirations. Second, the positive impact of school support on children's educational aspirations is significantly greater than the negative impact of risk factors. Lastly, the impact patterns of risk factors and school support on vulnerable children's educational aspirations exhibit significant heterogeneity across different household registration types and academic performance levels, but there is no significant difference between genders. This study confirms the adverse impact of risk factors on educational aspirations among vulnerable children, while concurrently validating the positive role of school support in fostering educational aspirations, thereby expanding educational expectancy theory's framework regarding vulnerable populations.