Aim: The aim of the present study was to investigate whether behaviours typical of working memory problems are associated with poor academic attainment in those with attention-deficit-hyperactivity disorder (ADHD), as well as a non-clinical group identified on the basis of working memory difficulties. Method: Children clinically diagnosed with ADHD-combined (n = 31; mean age 9y 7mo, SD 12mo; 27 males) were matched with 44 low working memory children (mean age 9y 4mo, SD 15mo; 32 males) and 10 healthy controls (mean age 10y, SD 12mo; 5 males). Working memory behaviour was measured using the Working Memory Rating Scale (WMRS) and academic attainment was assessed with standardized tests of literacy and numeracy. Results: The majority of children considered by their teachers to have problematic behaviours performed poorly in literacy and numeracy. When the whole sample were split into two groups on the basis of their working memory behaviour (on the WMRS), the "At Risk" group performed significantly worse in academic attainment. Interpretation: As children with ADHD and a non-clinical group exhibit classroom behaviour typical of working memory problems, early screening to prevent subsequent learning difficulties is important. The use of the WMRS allows educators to draw on their expertise in the classroom for early detection of children with working memory failures.