This paper examined grades 5 and 6 students' participation in wikis while writing reports on social studies topics. An analysis of eight wikis showed that students represented meanings they had constructed about their topics by engaging in knowledge telling practices (e.g., introducing, stating, or repeating information or an idea and developing previous ideas with examples, statistics or other information) more frequently than they engaged in knowledge transforming processes, such as drawing conclusions, identifying cause-effect relationships, or making inferences or judgements. Our research shows that Bereiter and Scardamalia's model (1987) is useful to inform the development of tools for assessing students' demonstration of their understanding of concepts in content area writing.