Mathematics subjects taken in the senior phase of secondary schooling involving the study of calculus, referred to here as advanced mathematics subjects, provide the necessary foundation for an extremely broad range of professions, including Science, Technology, Engineering and Mathematics (STEM) disciplines. In Australia, students from disadvantaged backgrounds are over-represented among those who do not meet national and international benchmarks in mathematics. This finding suggests that these students are less likely than their peers from more privileged backgrounds to study advanced mathematics subjects in their final two years of schooling. Given the importance of these subjects for broadening post-school options, it is crucial to identify practices that appear to be effective in promoting sustained interest and engagement in mathematics among students from disadvantaged backgrounds. Despite a national trend of declining enrolments in advanced mathematics subjects, some schools in low socioeconomic areas have experienced increased enrolments in these subjects. This paper reports on some preliminary findings of a study that investigated teaching and schooling practices in the early secondary years in one such school. The purpose of this paper is to present a comprehensive case study of this school that identifies personal, social and institutional influences that might impact on students’ future subject choices. Data sources were relevant school documents; semi-structured interviews with selected administrators, teachers, students and parents; and lesson observations. A person-in-context framework was constructed to analyse students’ engagement in mathematics. From this perspective, engagement in mathematics is seen as socially constructed through the interplay between individual and social/institutional influences. Data were analysed to identify factors at the personal, social and institutional levels that may contribute to engagement in mathematics at the case study school. The findings reported in this paper have a particular focus on the institutional level. Four themes were identified: curriculum organisation across Year levels; staffing of mathematics classes; culture of the mathematics department and provision of appropriate support for students. The case study presents a thorough description of identified effective practices in this school and explains how and why these practices work in this school context. The findings contribute to identifying ways to promote sustained engagement in mathematics, especially for students from disadvantaged backgrounds. Further research is needed to develop case studies for additional schools in low socioeconomic areas that have experienced increased enrolments in advanced mathematics subjects so that common themes and differences can be identified.