This study forms part of a longitudinal research project whose aim is to determine the extent to which immigrant students' social and personal networks could empower their academic careers and have an impact on their persistence in school and their academic success. The study uses the egocentric approach of social network analysis to reach a new level of understanding of successful academic careers and of the vulnerability of immigrant students in secondary school. The paper demonstrates the potential of this approach, which has led to the development of methodological processes and the creation of instruments for measuring and analysing the structures, patterns and forms of interaction that emerge from the ties among the different actors. The results show that the students' systems of relationships (family, school and community) constitute an intermediate level in which the dynamic, coordinated nature of social and personal networks' functions of socialization, contact and decision-taking are expressed. Furthermore, the results enable us to evaluate the impact of social networks on students' academic careers.