Objective: With reference to an epidemiological sample of adolescents and young adults the impact of different models on the number of children classified as having specific spelling problems is investigated.
Method: Using the same set of data, the effect of alternative definitions and methodological procedures on the prevalence of specific spelling retardation is shown. The virtual consequences of various norm-orientated definitions of cases is discussed with reference to external empirical criteria.
Results: Particularly, obsolete norms lead to a large overestimation of cases. In the present study case definitions of specific spelling retardation based on substantial criteria result in prevalence rates between 6 and 9 percent. Academic achievement is considerably affected by persisting specific spelling problems and the attendance of secondary schools is rare, in spite of sufficient nonverbal intelligence.
Conclusions: Because of the high impact of spelling ability for educational success, dyslexic children need help by early intervention. Furthermore scholastic promotion is necessary to enable a school carer appropriate to the intellectual possibilities of the child.