This study explores how competence systems can support curriculum continuity and enhance STEM preparedness across educational transitions, particularly from upper secondary school to higher education. The research focuses on Estonian students’ decision-making regarding elective subjects, their perceived readiness for university-level STEM studies, and the structural effectiveness of the current curriculum. A mixed-methods design was employed, combining quantitative survey data with qualitative thematic analysis of open-ended student responses and key educational documents, including the 2023 Estonian National Curriculum, IGIP and IEA competence frameworks. Findings reveal that while 38% of students choose electives aligned with future studies, the majority select based on personal interest. Students rate their learning skills as generally good yet report specific gaps in self-regulation. Students also identified curriculum shortcomings, such as limited practical life education and unclear expectations for university preparedness. By triangulating student perspectives, statistical trends, and curricular frameworks, the study highlights the potential of competence systems to better inform elective planning, enhance curricular alignment, and improve retention in STEM fields. Recommendations include integrating future-focused guidance and strengthening the coherence between school curricula and university expectations to reduce student dropout rates.