Cross-community collaboration which expands community members' interaction to a larger social scale plays a crucial role in increasing information exchange and extending inquiry learning. This dissertation uses a design-based research approach which aims at testing a multi-level emergence design in multiple learning communities. This design serves the urgent need to enable students' idea sharing and build-on with members from other communities who have similar interests for mutual learning and collective knowledge advances. A mixed-methods research approach was used to investigate the cross-classroom collaboration over three successive years: pilot 1, study 1, and study 2. Knowledge Building Theory and pedagogy guides in learning and teaching practices. The fifth grade Knowledge Building communities studied human body systems with the support of the Knowledge Forum and the Idea Thread Mapper online platforms. As students conducted focused inquiry and discourse within their own community, they posted their learning reflections to a cross-community space and read other's learning reflections from both current and previous years. In study 2, the classrooms further participated in an ongoing cross-community discussion in addressing a challenging question. Findings suggest that the learning reflection takes the form of the Journey of Thinking in this study and enables information transfer among the network of communities. Students wrote and posted their Journey of Thinking to capture substantive idea progress and deepening questions that had emerged from their inquiry. Students showed solid reflections in their Journey of Thinking with the help of Knowledge Forum and Idea Thread Mapper. The multi-level structure allows students' social interaction in a broader landscape with their peers. Analyses of the classroom conversations elaborated how students built on the insights gained from the cross-classroom interactions to develop deeper understandings in their home classroom. Analyses of teacher interviews and classroom metacognitive meeting reveal the teachers' roles to contextualize the purpose of the cross-classroom activities, support Journey of Thinking reading and writing, and scaffold cross-classroom connection and conversation. The results also provided an elaborated account of the ongoing collaboration in the cross-community space. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]