The purpose of this research article is to understand a quiet student's leadership in small groups using "cultural tools" as analytic framework. Cultural tools of James V. Wertsch's expanded Vygotsky's notion of mediation, deeply rooted in the sociocultural theory. This article illustrated the origins, meanings and applications of the cultural tools. The study took place in a sixth grade class of an urban and diverse middle school located in the Northwestern United States. In order to understand the subject's participation, teacher's instruction during literature circle, and the group interaction was analyzed and understood through the framework of cultural tools. The result showed that the student's leadership was mediated by tools the teacher provided, purposefully or unintentionally; yet the student needed further support in gaining power. The significance of the study is to provide perspectives on teaching and learning by placing them in the context and examining the intertwined relationship between teacher's instruction and student behaviors.