A sociocultural view of learning positions teachers as mediators who teach a curriculum that reflects what is valued by society. In this paper it is proposed that a specific focus on mediating relational agency to support collaboration further builds teacher and student capacity for learning. Relational agency is a two-way process, to become responsive so you can both receive and give support to peers. Peer interaction supports the development of communication, social and emotional competencies required for effective collaborative learning. The aim of this paper is to reflect how evidenced based social practices promoted relational agency in a collaborative classroom. These social practices can be adapted by other teachers interested in this approach with their students. The data are drawn from three linked, consecutive year-long projects conducted by the teacher/researcher with her students and teacher/colleagues whom she mentored. Rogoff's analytical planes provide a framework to analyse the qualitative data. The findings are presented as four case studies related to bullying, conflict resolution, student leadership and teacher mentoring that illustrate relational agency in action. Further research is necessary to understand how to support teachers for 21st century learning, within the context of traditional schools where the status quo is well established.