<p>With the increasing emphasis on technical and design skills, the development of K-12 students in project-based and practice-oriented learning environments, such as STEAM competitions, has become particularly important. In these technologically complex and open-ended design challenges, K-12 students often have weaker autonomy, which can lead to poor learning outcomes. Helicopter parenting (HP) and peer support (PS) play significant roles in shaping their learning outcomes. While previous research has primarily focused on the delayed effects of HP during the school years on students who have just entered college, with little investigation into K-12 students who have weaker autonomy in the context of the technology and design competition, especially STEAM competitions. Research on the three influencing factors of attainment acquisition in STEAM competitions for K-12 students (parents, individuals, peers) is also relatively limited. This study, set against the backdrop of a STEAM competition, surveyed 281&#xa0;K-12 students to explore the relationship between HP and students’ attainment. In this team-based, design-intensive environment, we investigated the mediating role of achievement motivation (AM) between HP and students’ attainment, as well as the moderating role of PS between AM and STEAM attainment, based on the self-determination theory. The results showed that HP was positively related to K-12 students’ AM and ultimate attainment in STEAM competitions, and also verified the partial mediating role of AM between HP and attainment acquisition. Additionally, AM was positively related to attainment, and PS significantly moderated this process. These research findings reveal how social factors and individual motivation interact in STEAM competitions, providing practical insights for parental involvement strategies in technology and design education and for the construction of supportive peer networks in design-based learning.</p>