The use of clustering strategies in semantic and phonological fluency was tested in children in third (age 8–9) and fifth (age 10–11) grades. To analyze the development of clustering strategies in the fluency task, the latency to the first word and intervals between clustered and non-clustered words were recorded. Semantic fluency was greater than phonological fluency in both age groups. Children in fifth grade had greater semantic and phonological fluency than children in the third grade, concomitant with an increase in number of clusters, but not in cluster size. The greater facility of the children with semantic fluency was confirmed by a shorter latency to the first word, and significantly shorter intervals between clustered words compared to non-clustered words. Girls had shorter latencies to the first word and made more phonological clusters in the semantic task than boys. The increase in cluster number and concomitant increase in fluency in older children might be related to the development of cognitive flexibility. These data suggest that measurement of clustering strategies in the verbal fluency task can be used to assess executive function deficits in children with acquired or developmental neurological impairment or attention deficits.