The shortage of qualified STEM teachers and researchers in these fields can be recognized as an existing and forthcoming problem. The aim of the present study was to explore the influence of the content of STEM subjects Biology, Chemistry, Informatics, Mathematics, Physics, and Technics and Technology and corresponding classroom experiences, as perceived by students, in elementary and general secondary schools on student's career aspirations and ambition to work as researchers or educators as their career choice. The sample comprised 552 upper general school students (ages 17 to 19) in their last two years before entering University. We hypothesized that a combination of general interest in each of the six listed disciplines, together with the content taught in elementary and upper secondary school, together with respective classroom experiences, will influence career aspirations expressed by ranking their wish to work as educators or researchers. With the use of Structural Equation Modeling, we revealed that Biology, Chemistry, and Physics can statistically significantly explain career aspirations to become a researcher. However, Informatics, Mathematics, and Technics and Technology cannot. None of the listed disciplines positively predicts career aspirations to become an educator. From the correlation between ranked aspirations toward a research and an educational career (r 5 -.03; p 5 .964), we can conclude that most of those who considered a career as a researcher as a plausible option do not share the same opinion about a career in education.