Musical agency refers to individuals' capacity for autonomous action within musical contexts, encompassing both individual dimensions such as self-identity, self-regulation, and musical perception, and collective dimensions including social relationships and community belonging (Karlsen, 2011). Sutela et al. (2021) further conceptualize musical agency as an embodied process involving creative decision-making, peer interaction, emotional expression, and self-perception as a capable musician. Despite growing scholarly interest, quantitative and mixed-methods approaches to measuring musical agency in culturally grounded classroom settings remain limited.Korean traditional folk songs (minyo) possess rich aesthetic dimensions through regional pitch collections, melodic contours, sigimsae (ornamental vocal techniques), and distinctive expressive qualities. However, current elementary music education in Korea tends to reduce these heritage songs to mechanical imitation, limiting students' opportunities to exercise musical agency. The 2022 revised Korean national curriculum provides a supportive framework for integrating aesthetic engagement with agency development.This study designed and implemented an aesthetic education program centered on Korean traditional folk songs for fifth-grade students. The program incorporated aesthetic listening to regional folk songs, sigimsae exploration, collaborative call-and-response singing (megigopatgi), creative lyric adaptation connected to personal experiences, and improvisatory vocal expression. These activities aimed to shift students from passive imitation toward active musical engagement through creative decision-making, peer interaction, and emotional expression.A quasi-experimental pre-post design with mixed methods was adopted. A total of 200 fifth-grade students across ten classes participated, assigned to experimental and control groups. Musical agency was measured using a validated Musical Agency Scale for Elementary Students, administered before and after the ten-session intervention. Paired-samples and independent-samples t-tests were conducted for quantitative analysis. To complement the statistical findings, qualitative data were collected through teacher observation assessments and student learning journals, providing richer insights into how students experienced and expressed musical agency throughout the program.Results indicated statistically significant improvements in the experimental group's musical agency scores across both individual and collective dimensions, while the control group showed no significant changes. Qualitative findings from teacher observations and student journals corroborated these results, revealing that students increasingly demonstrated creative decision-making, voluntary peer interaction, and self-recognition as capable musical agents. This study provides convergent evidence that culturally grounded aesthetic experiences in Korean traditional folk song education can transform students from passive imitators into active musical agents, offering practical implications for curriculum design that honors heritage while empowering young learners.