Background: Researchers have previously commenced examining the degree of concordance between parent proxy and child self-reports on health-related quality of life (HRQOL) of many disease and impairment populations. Objects: To explore the differences between parent proxy and child self-reports on the HRQOL using Korean version of KIDSCREEN-10 questionnaires for applying to elementary school children and their parents who participated for a school-based wellness program. Methods: The focus groups were recruited for a school-based wellness program by implementing the following wellness services: 1) referring to a screening session for detecting potential posture-related musculoskeletal problems and 2) recommending home exercise programs. Before a primary field testing for the program, two focus groups were formed with a group of 9 parents and their 9 elementary school children aged 8–10 years of age. The parent proxy and child self-report versions of KIDSCREEN-10 questionnaires were administered to both groups after completion of the wellness program. Item level Rasch rating scale analysis was applied to compute logit scales of KIDSCREEN-10 questionnaire. Intraclass correlation coefficients (ICCs) and scatterplot of item difficulty between two reports were analyzed. Results: For fit statistics of parent proxy report, all items except 4 items (i.e., psychological well-being, mood/emotions, self-perception, parent relation) were found to be acceptable. For fit statistics of child self-report, all items except 3 items (i.e., psychological well-being, autonomy and home life) were acceptable. The relationship between two reports using ICCs were ranging from weak to very strong at p = 0.05 (i.e, ICCs = 0.011 to 0.905). Scatterplot analysis between two reports showed a major disparity on self-perception item at 95% confidence intervals. Conclusion: Both item level analyses and ICC comparisons provided a disparity between parent proxy and child self-reports of the HRQOL on self-perception item after competing a school-based wellness program. Therapist should consider the item as part of the HRQOL assessment.