This study verified validity and reliability of the School Function Assessment (SFA) using Rasch analysis in South Korean school-based occupational therapy sites serving children with intellectual disabilities and others. Participants were 103 elementary school children (grades 1 through 6) with disabilities. Rasch analysis revealed several misfitting items. Difficulty levels of items, presented in hierarchical order, were very different from those found at the time of development of the SFA. Results for the rating scale fit showed that a 4-point scale, rather than the existing 6-point scale, was more appropriate for several parts of the SFA in the Korean context. Separation reliability ranged from good to very good, with coefficients from 0.85 to 0.99. This study contributes to the literature by verifying the reliability and validity of the SFA for students who need school-based occupational therapy in Korea using Rasch analysis, with a focus on applying it to children with intellectual disabilities and autistic spectrum disorders. For more efficient application of the SFA in South Korea in the future, it remains necessary to modify the misfitting items, rearrange their difficulty levels, and properly adjust the rating scales rather than evaluating items by literally translating them into Korean.