This research compares the curricula of general upper secondary education systems in France, Italy, and in England. It starts from the observation that, in large-scale international comparisons, high school curricula are considered equivalent since they fundamentally share the same political and educational mission: preparing students for higher studies. However, high schools are indeed characterized by substantial curricular variations, which are almost ignored in these comparisons. As contemporary international studies are founded on issues of knowledge and governance among the various education systems, this research adopts an analytical and comparative approach capable of including those curricular variations. In this respect, this research examines, firstly, the interdependent relationship between the founding principles and the organizing principles that inform the different high school systems. Secondly, it analyzes the effects that curricular structures may induce on their founding missions. This is achieved through a comparative and systematic analysis of historical evolutions in high school curricula and their organizations. The three curricula compared in this research have been selected as their organizing principles are particularly contrasting: the English GCSE - Advanced Levels, the French séries générales du lycée d'enseignement général et technologique, and the Italian scientific and classic liceo. This study collects and analyzes data gathered from different documentary sources. The primary source is an in-depth review of a selection of official documents detailing the historical evolution of the three high school systems and their organizations. This analysis is supplemented by the consultation of official reports evaluating the three educational systems, and by conducting interviews with pupils and teachers of three high schools, one for each country involved in the study. International comparison was the main research method adopted to study the selected data. It was employed throughout the thesis as a tool both to identify and then to interpret the variables considered in the analysis. In addition, a contribution of this dissertation consists in proposing an innovative research tool: the curriculum experience. This notion enables analysis and comparison of the relationships between the curriculum components and the meanings associated with them. This investigation shows that, despite the fact that the three high school curricula share the same founding principles, their structure can actually have an influence on how their common political-educational mission is understood and implemented. The priority of the general upper secondary education in England is to adequately prepare for university studies; in Italy, the liceo is mainly conceived as the final stage of a common and general curriculum that begins in the general lower secondary schools; in France, the focus is to differentiate the educational tracks of pupils in the light of the segmentation featured in the French higher education system. The findings of this research, along with the methodology employed, give insight into the systemic dimension of high school curricula, an aspect that has been largely underestimated by both decision-makers designing the curricula and by the institutions producing international comparisons. In addition, this research gives a valuable contribution to the development of a comparative approach to education analysis by giving evidence of the heuristic potential of comparative methods. It also clarifies the purpose of the general upper secondary education systems, as well as their possible evolutions, in the context of the democratization of higher education.