This work is based on a partial data from the first author's master thesis. Objectives: Conversational skills play an important role in social aspects such as the peer relationships and academic achievement of school-aged children. The purpose of this study was to investigate developmental differences according to grade for primary school students in the 1st, 3rd, and 5th grade. Methods: The participants were a total of 30 children, 10 children per grade. Conversation samples were collected individually by the examiner according to procedure of Hallym Conversation & Pragmatic Assessment Protocol. In terms of engagement indicator, the frequency of turn-taking, frequency of utterances per turn. Additionally, in terms of topic indicator, the total number of topics, frequency of turn per topic, rates of maintenance and rates of change were measured. Results: The results were as follows: in engagement indicator, significant difference was observed in the frequency of utterances per turn. In topic indicator, there were significant differences in the total number of topics, frequency of turn per topic, rates of maintenance, and rates of change. Conclusion: The results of this study showed that as school-aged children's grade increased they were able to converse over a given topic with more consistency. These results help elucidate the development of conversation in elementary school-children and can be used as materials for the assessment and intervention of children with disabilities.