Abstract
BACKGROUND: Peer-assisted learning (PAL) is an established approach in medical education, yet variability in teaching quality persists when peer tutors lack structured pedagogical support. This study examined whether integrating a structured formative assessment framework could enhance peer tutors' teaching performance, teaching self-efficacy, and reduce teaching anxiety, as well as improve first-year students' knowledge, academic motivation, and self-efficacy. METHODS: A quasi-experimental, parallel- group study was conducted in three medical universities in Guangdong, China (2024-2025). Final-year medical students (n = 122) served as peer tutors and were allocated to an intervention (n = 61) or control groups (n = 61), each supervising 6-8 first-year students (total first-year students initially = 850; final analytic sample = 820) (intervention n = 411; control n = 409). The intervention integrated validated formative assessment tools-Mini-Clinical Evaluation Exercise (Mini-CEX), Direct Observation of Procedural Skills (DOPS), and Reflective Teaching Journals-alongside faculty feedback and self-reflection. Data were analyzed using linear mixed-effects models (LMM) accounting for student-tutor nesting. False discovery rate (FDR) correction was applied to control for multiple testing. RESULTS: Significant group × time interactions favored the intervention group across all outcomes. Students taught by intervention-group tutors showed higher post-test knowledge (7.93 ± 0.31 vs. 5.28 ± 1.10; F = 54.9, p < 0.001, η(2) = 0.18) and greater academic motivation and self-efficacy (both p < 0.001). Peer tutors demonstrated higher teaching self-efficacy (72.48 ± 5.73 vs. 69.13 ± 5.91; F = 22.3, p < 0.001, η(2) = 0.15) and lower teaching anxiety (2.34 ± 0.33 vs. 2.65 ± 0.39; F = 17.1, p < 0.001, η(2) = 0.14). Post-test performance measures (PES-TBL, Mini-CEX, DOPS) were consistently higher in the intervention group (all p < 0.001). Qualitative reflections revealed challenges in communication and confidence but documented progressive improvements in interaction and teaching clarity. CONCLUSION: This study provides preliminary evidence that integrating structured formative assessment into peer-assisted learning enhances tutors' instructional competence, strengthens self-efficacy, and reduces teaching anxiety, while simultaneously improving students' motivation and learning outcomes. Embedding formative assessment within PAL may represent a feasible and scalable strategy to improve teaching quality in medical education.