In order to investigate the stances of high school students and researchers toward STEM subjects, we introduce the methodology of forma mentis networks -- free association networks enriched with affective attributes that represent how people conceptually perceive and structure their stance toward a given topic. In this paper, we constructed separate forma mentis networks for ($N_s=159$) Italian high school students and ($N_r=59$) interdisciplinary professionals and researchers in order to investigate how these groups differed in their mental associations and emotional perceptions of STEM subjects. At the global scale, STEM concepts occupied central positions in students' forma mentis network, suggesting that students understood the general importance of such topics in science. At a microscopic scale, although the concept of "science'' was positively perceived in both the students' and professionals' forma mentis networks, students not only perceived STEM concepts such as "physics'' and "mathematics'' as negative but also associated them with other negative STEM-related concepts. This aura of negative emotional associations towards quantitative STEM subjects was absent in professionals. Cross-validation with external datasets suggested that the negative emotional aura in the forma mentis network of students might be attributed to science anxiety. Further consideration of the semantic associates of maths and physics indicated that their negative aura may originate from a negative, dry perception of the technical methodology and quantitative tools frequently taught in these subjects (e.g., "function'', "integral'').Whereas students associated mathematics and physics with quantitative tools, professionals linked the same disciplines to more general and creative aspects of science and displayed a positive stance towards these concepts. Overall, our results underline the crucial importance of emphasising nontechnical and applied aspects in the teaching of quantitative disciplines, highlighting the necessity of establishing interdisciplinary links between science, the complexity of the real-world and creativity in order to enhance the impact of STEM education and outreach activities.