The aim of this article is to elucidate how teacher researchers use a theoretical framework as mediated tool to create boundaries in communities of research practices (CoRPs) and how this effects student learning. If, and in what way, knowledge developed in one practice can be used to inform the next is also examined. Two teacher researchers implemented two CoRPs each, one as internal participant and one as external participant. In total, 202 students, 22 teachers, 2 teacher researchers, and 1 researcher participated. The qualitative analysis is framed by Wenger's three boundary dimensions: engagement, imagination, and alignment. The results show that teachers' actions in the second practice, no matter if they were internal or external participants, are characterized by a higher degree of security and knowledge and the lessons implemented are more effective regarding the students' learning outcomes than in the first. The results show that knowledge develops in an interaction order regardless of the internal or external community order. The result from the first team informs the starting point for the second team, and knowledge boundaries are transferred by the teacher researcher from one CoRP to the other.