<![CDATA[Students with mild intellectual disability struggle with addition because of difficulties understanding abstract concepts, while purpose-built teaching aids may be unavailable in special schools with limited facilities. This study examined the effect of coin media on the addition skills of a third-grade student with mild intellectual disability at SKh Pelangi Anakku, Tangerang City, and whether the acquired skill persisted after withdrawal. A quantitative Single Subject Research approach employed an A₁–B–A₂ design with five sessions in each phase. The target behavior was completing five addition problems involving whole numbers from 1 to 15 without regrouping. Data were collected through tests, observation, and documentation. Instrument consistency was maintained across phases, and the student’s work was reviewed with the classroom teacher. Visual analysis within and between conditions covered trend direction, stability, level change, and overlapping data. The mean score increased from 44 during the first baseline to 72 during intervention and 80 during the second baseline, representing an 81.82% increase. The 20% overlap between baseline phases indicated improved attainment. However, the level change when coins were introduced was zero, while overlap between intervention and the second baseline reached 80%; therefore, the effect of coins cannot be fully separated from the consistent worksheet format. Observations showed that the student progressed from manipulating coins to independently counting on fingers, and performance persisted after withdrawal. Coin media therefore served as a bridge toward independent counting rather than a permanently required aid. Teachers in resource-limited special schools may use available objects alongside predictable worksheets and gradual withdrawal.]]>
