This paper describes the design of a technology platform for supporting content-independent collaborative mobile learning in the classroom. The technical architecture provides mechanisms for assigning different content or materials to students and then guiding them to form groups with other students in which the combination and integration of their content satisfies some pre-assigned critera or goal. The uniqueness of this lies in the dynamic forming of collaborative groups rather than having fixed or preassigned groupings of students for doing collaborative work. We present the theoretical underpinnings of our approach, the initial design of the software and the iterative cycles of a Design-based Research (DBR) approach that tries out the continuously being-refined design with primary school students. Feedback and data collected from observing students' actual learning behaviors and motivations in the cycles were used to propose a new cycle of the system and user-interface redesign. Such school-based trials provided demonstrations of the platform in supporting two content-specific learning applications, namely in mathematics and Chinese language learning activities in a primary school setting. They show the enactment of collaborative scaffolding comprising peer, technological and teacher scaffolding in supporting the students' formation of groups, and their collaboration and learning.