The purpose of this study was to explore possible developmental changes of vocational high school students’ scientific inquiry competence while they learned within the “Mechatronics” inquiry-based curriculum and instruction. A case study approach was employed in this study, while multiple resources of 77 11th graders’ learning were collected and analyzed by using the editing analytic techniques. During the process of this two-year study, there were 11 changes of students’ competence extracted from the data collected. These changes were inducted into 6 categories of scientific inquiry competences and then finally formed three themes, “basic competence, advanced competence, and critical competence”. The result of this study was reported as a developmental triad of students’ scientific inquiry competences. Based on discussions, as teachers, we have to actively implement the real-life problem-solving teaching practice to enhance students’ scientific inquiry competences. The findings of this study also provided the insight that how teachers understood the scope and sequence in designing inquiry-based curricula. Finally, the dialogue between the findings and the literature reminded us that students’ scientific inquiry competences could not be cultivated in a short time; instead, a long-term and context-driven curriculum design is the cornerstone to develop their competences for future learning and life.