Family socioeconomic status (SES) has a significant influence on children's academic success and is related to parents' attitudes toward education. Moreover, according to the expectancy-value theory, parental expectations are linked to their children's perceptions of school, which, in turn, influences the way their children invest themselves in education. In this study, we aimed to test a part of the theorical expectancy-value family socialization model that links family SES and parental expectations and explore their influences on children's mathematics self-concept and achievement. This study was conducted in the Chilean context, which is characterized by strong neoliberal educational policies that induce a strong relationship between family economic resources and children's educational trajectories. We utilized a longitudinal design, and our study sample (N = 157,814 Chilean students) came from a national assessment that was conducted from 2007 to 2013 when students were in their 4th, 8th, and 10th grades. Our results showed that, while controlling for children's previous mathematics achievement, their final mathematics achievement was influenced by children's mathematics self-concept, the family socioeconomic and educational context, and parental expectations regarding their children's academic achievement. Our findings also highlighted that Chilean parents base their expectations on parents' capacity to support their children's education as much as on their children's previous academic achievement.