Background The purpose of the current cross‐sectional study was to examine the developmental progression in working memory (WM) between the ages of 9 and 16 years in a large sample of children with mild to borderline intellectual disabilities (MBID). Baddeley's influential WM model was used as a theoretical framework. Furthermore, the relations between WM on the one hand, and scholastic skills (arithmetic and reading) on the other were examined. Method One hundred and ninety‐seven children with MBID between 9 and 16 years old participated in this study. All children completed several tests measuring short‐term memory, WM, inhibition, arithmetic and single word reading. Results WM, visuospatial short‐term memory and inhibition continued to develop until around age 15 years. However verbal short‐term memory showed no further developmental increases after the age of 10 years. Verbal short‐term memory was associated with single word reading, whereas inhibition was associated with arithmetic. Discussion The finding that verbal short‐term memory ceases to develop beyond the age of 10 years in children with MBID contrasts with results of studies involving typically developing children, where verbal short‐term memory develops until around age 15 years. This relative early developmental plateau might explain why verbal short‐term memory is consistently considered weak in children with MBID.