Background <p>Academic resilience, defined as the capacity of socio-economically disadvantaged students to achieve at high academic levels, is a key indicator in international education policy. Large-scale assessments like the Programme for International Student Assessment (PISA) routinely report the prevalence of academic resilience as a summary measure of system quality, combining efficiency (high achievement) and equity (reduced socio-economic disparities). Building on this approach, comparative research has sought to identify school factors that promote resilience, treating it as a property of schools and systems rather than an individual trait. However, most existing evidence relies on cross-sectional data and contemporaneous measures of school characteristics, which may be confounded by other factors, particularly students’ prior achievement.</p> Methods <p>We investigate whether academic resilience in Italy reflects the characteristics of the upper-secondary school that students attend at age 15 or earlier achievement differences. We use unique longitudinal data linking Italian students’ achievement in PISA 2018 (grade 10) to their standardized test scores from grade 8 and 5 (INVALSI, grades 5 and 8; <i>N</i> = 5,323). Since grade 8 marks the end of lower secondary education in Italy, just before students are tracked into different upper secondary schools, controlling for grade 8 achievement allows us to isolate the contribution of the two years of upper secondary schooling captured in PISA. Following OECD reporting, academic resilience is defined as being in the lowest quartile of socio-economic status and the top quartile of mathematics achievement in grade 10. We describe achievement trajectories by socio-economic group and use multivariate models to assess the relative contribution of key school factors identified in PISA (e.g., disciplinary climate or truancy) and prior achievement to academic resilience.</p> Results <p>Socio-economic disparities in mathematics achievement emerge early in the Italian education system. Grade 8 achievement is the strongest predictor of the likelihood that disadvantaged students will be academically resilient in grade 10. Most school-level factors at the upper-secondary level that are measured in PISA show weak or non-significant independent associations once prior achievement is accounted for. Academic success in grade 8 is more predictive of later success for socio-economically advantaged students. Initially high-achieving but less socio-economically advantaged students are more likely to fall behind in their educational careers.</p> Conclusions <p>Academic resilience in upper-secondary schools in Italy appears to reflect achievement differences that are established early and evolve over students’ academic careers. The cross-sectional indicators of resilient students or resilient schools measured in PISA at the upper-secondary level should therefore be best viewed as descriptive indicators rather than measures of school effectiveness.</p>