Background. The background of the present study includes analysis of the understanding of active and passive grammatical constructions (GCs) in Russianspeaking aphasic patients and in children aged 3, 4 and 5 years (Akhutina, 1989; Akhutina, Velichkovskiy, & Kempe, 1988). Data regarding the reorganization of the children's strategies are further compared to GC understanding in children speaking different languages, and their interpretations. Objective. To analyze the variable mechanisms of understanding of rever sible GCs in primary-school-age children, namely, to reveal individual differences in reliance on word order or case endings. Design. Ninety-three first-graders, 93 second-graders, and 63 third-graders underwent a neuropsychological assessment and computer-based sentence-topicture test of their understanding of reversible GCs of active/passive voice with direct/reverse word order. The "productivity" of understanding GCs (percent of correct responses) was analyzed through cluster analysis. Results. The cluster analysis divided the children into four clusters. Cluster 1 consisted of eight children with low productivity, who were excluded from further analysis. Cluster 2 was characterized by low productivity in passive direct constructions (Group 1); Cluster 3 comprised children who had low productivity in passive reverse sentences (Group 2). Cluster 4 included children with good understanding of all GCs (Group 3). Between-group differences in productivity and time of correct responses in GCs, as well as neuropsychological indexes, were revealed. Conclusion. The results are consistent with the following hypotheses: (a) Group 1 relies on the rule "The first noun is the agent", whereas the other two groups use morphological marking; (b) Group 1 is the weakest neuropsychologically, and syntactic understanding processes involve a more diffuse activation of the brain in this group, compared to more successful children; (c) changes in response times from the first to the second grade are under the influence of cerebral changes induced by reading acquisition.