In this study, children (ages 7-12) of average intelligence who had learning disabilities (LD) (n=29) and typical children (n=30) were individually tested in a task that investigated the development of proportional structures of thought. In addition, mathematical knowledge was assessed on the Woodcock-Johnson Tests of Achievement-Revised (WJTA-R). In this cross-sectional design, students in both groups coordinated increasingly more complex relationships among the elements of the problems as a function of grade. However, significantly fewer children with LD had yet constructed the second-order logical structures necessary to act on problems using multiplicative and pre-proportional reasoning. No children in either group demonstrated formal proportional reasoning, although a small minority evidenced qualitative proportional reasoning. On the applied problems test of the WJTA-R, the students with LD performed significantly below same-aged peers, although they achieved approximately at grade level on this task. Performance differences between the two groups on computation approached significance. For both groups, the explicitly taught procedures to solve computation and word problems as measured on the WJTA-R failed to represent accurately the degree of operational logic in children's biologically based structures of logical-mathematical activity. (Contains 35 references.) (CR)