Abstract
The research reported in this paper was designed in a cross-sectional perspective to examine differences between mathematically disabled children (MD children) and mathematically normal children (MN children). Examined was the pattern of development that unfolds when the children move up through primary school, as reflected in their level of performance, in the discrepancy between their performance on simple number-fact problems compared with simple word problems, as well as in their use of task-specific strategies, identified as material, verbal, and mental strategies. The MN children's performance gradually improved from the second to the sixth grade and showed progression from strategies based on use of material through verbal strategies to mental strategies. The MD children's performance showed a course of development that had almost peaked in Grade 2, and their problem solving reflected inflexible use of a narrow register of different task-specific strategies characterised by functional efficiency dependent on problem type. The MD children's consistent use of material strategies was in accordance with the view that these children had both fact-retrieval problems and working-memory problems, and it indicated absence of an adequate domain-specific knowledge base of task-specific strategies. The findings highlight the MD children's need for mathematics instruction to move from focus on computation to strategy-learning activities.