Quantum information science and technology provide contemporary contexts for teaching and learning foundational principles of quantum physics by accessing them via two-state systems. In this study, a teaching approach based on a Spin First approach is developed for introducing quantum physics at lower secondary level in a qualitative way. The teaching approach follows research-based design principles. It introduces electron spin as an exemplary two-state system and embeds basic concepts of quantum physics related to the context of quantum computing. To examine the feasibility and suitability of this teaching approach in principle and to formatively evaluate the content structure, semi-structured individual interviews with alternating intervention and survey phases (“Teaching Experiments”) were conducted with N=11 grade 9 students. Learning outcomes were assessed based on an evaluative qualitative content analysis, and further general assessments regarding learning difficulties, prior knowledge and student assessment could be derived based on the interviews. The results of this evaluation reveal the approach to appear suitable for the addressed target group. Students seem to qualitatively understand foundational principles of quantum physics, and no significant mixing of classical and quantum physical principles is observed. Nevertheless, evidence of potential learning difficulties becomes apparent (e.g., adequate use of language and verbal reasoning, unreflective reasoning based on hidden variables, inert knowledge and lacks of prior knowledge), which in turn results in amendments to the teaching approach and supports the further development of ready-to-use teaching materials and the preparation of an extensive field study in the future.