Astronomy is seen as a "gateway" science, inspiring students to pursue Science-Technology-Engineering-Mathematics (STEM) related careers. However, there is little evidence that students' attitudes towards astronomy remain stable over time. By integrating Self-Determination Theory (SDT) and Theory of Planned Behaviour (TPB), we identified three dimensions of students' attitudes towards astronomy - intrinsic, which refers to the enjoyment of studying astronomy, extrinsic, which refers to the will to pursue a career in astronomy, and utilitarian, which refers to the relevance of astronomy to society. We used these dimensions as indicators for a Latent Profile Analysis (LPA) to identify attitudinal profiles of 2650 Italian students in grades 9-13. We identified seven profiles, ranging from completely negative to completely positive attitudes. In particular, students enter secondary school mostly interested in astronomy and with a positive view of astronomy. By the end of secondary school, students have significantly lower attitudes towards astronomy in all three dimensions identified. From a theoretical perspective, our study shows that the SDT/TPB framework can be used to develop future instruments aimed at measuring students' attitudes towards science. From a practical point of view, our results call for better support for teachers to maintain students' attitudes towards astronomy throughout secondary school.