Pre-service mathematics teachers' integration of design thinking in STEM lesson plans: Insights from a qualitative case study

Mathematics is foundational in science, technology, engineering, and mathematics (STEM) education. Mathematics can foster problem-solving, quantitative reasoning, modeling, and creativity across disciplines. This study explores how pre-service mathematics teachers (PMTs) in a Design Thinking (DT)-focused course integrate DT into STEM lesson planning, the factors influencing this integration, and the challenges encountered during lesson planning. 55 senior PMTs at a state university in Türkiye participated in the study. Data were collected through DT-oriented, mathematics-focused STEM lesson plans and an open-ended questionnaire and were analyzed using content analysis. Findings reveal that while many PMTs maintained mathematics as a core component in their plans, the integration of DT was often partial and unbalanced. The Define, Ideate, and Prototype phases were predominant across most plans (>80%), whereas the Empathy phase was considerably less represented, appearing in only 20.8% of plans. In contrast, while the Test phase was incorporated into more than half of the lesson plans (54.2%), its presence remained substantially lower than that of the initial construction phases, reflecting a tendency toward linear product completion rather than sustained, iterative design optimization. Participants reported difficulties aligning DT phases with learning objectives, selecting appropriate materials, and designing effective assessment strategies. Despite these challenges, PMTs strongly believed in DT's potential to enhance student engagement, creativity, and real-world mathematical thinking. The study underscores the need for teacher education programs to provide more explicit scaffolding and practical tools to meaningfully embed all phases of DT within mathematics instruction.