To enable high school students, especially those interested in art and design-related careers, to improve their ability to integrate knowledge of science, technology, engineering, and mathematics (STEM) in their creative design practices and to be familiar with auto manufacturing, the development of a bridging curriculum, known as STEAM (science, technology, engineering, arts, and mathematics) using digital tools such as 3D printers, has been increasingly recognized as emergent and vital. As a bridging curriculum, it is essential to examine the curriculum with respect to high school and college students to highlight the differences in their knowledge and skills for improving curriculum development. Hence, we conducted a teaching experiment using a CO[subscript 2]-car engineering design curriculum in this study to analyze the learning outcomes of four groups of students (three 3D-printing groups: 108 high school students, 12 design college students, and 12 engineering college students; one handmade group: 36 high school students) to assess their competencies. The results of the present study highlight significant differences in creativity, forecast accuracy, race outcomes, and learning outcomes. Suggestions based on the results were generated to improve the curriculum. The findings in this study serve as a reference for the future design, development, and implementation of STEAM curricula.