The central feature of a written expression disorder is that skill falls substantially below that expected for the child's chronoligical age, measured intelligence, and age-appropriate education. Skill is measured by individually administered standardized tests. The disorder significantly interferes with academic functioning and daily living. There is generally a combination of difficulties in the child's ability to compose texts demonstrated by grammatical or punctuation errors writing sentences, poor paragraph organization, multiple spelling errors, and excessively poor handwriting. The diagnosis is generally not given with only spelling errors or poor handwriting. Letter and number reversals are not uncommon through age nine.
Less is known about this disorder and remediation in comparison with a Reading or Mathematics Disorder, especially in the absence of a Reading Disorder. Standardized tests are less well developed, except for spelling. The evaluation of written expression may require a comparison between extensive samples of a child's schoolwork. This is expecially the case for young children in the early elementary grades. Tasks in which the child is asked to copy, follow dictation, and compose spontaneously may all be necessary to establish the presence and extent of this disorder. There is some evidence that language and perceptual-motor deficits may accompany this disorder.
Difficulties may appear as early as the first grade, including poor handwriting or copying ability or inability to remember letter sequences in common words. This disorder is seldom diagnosed before the end of first grade because sufficient formal instruction has usually not occurred until this point in most school settings. It is usually apparent by the second grade. It is occasionally seen in older children and adults, and little is known about its long term prognosis.