Despite many years of research in CSCL, computers are still scarcely used in classrooms today. One reason for this is that the constraints of the classroom environment are neglected by designers. In this contribution, we present a CSCL environment designed for a classroom usage from the start. The system, called TapaCarp, is based on a tangible user interface (TUI) and was designed to help train carpenter apprentices. A previous study (Cuendet and Dillenbourg 2013) showed that the tangible nature of TapaCarp helped integrate it in the classroom environment, but that this did not guarantee a meaningful learning activity. In this article, we describe the process that led us to design a new learning classroom activity for the particular context of dual carpentry apprenticeships. One innovative aspect of the activity is that TapaCarp is used only for a small part of it. This contrasts with the mainstream CSCL approach that assumes that the system must be used from beginning to end of the activity. This new activity was used in a classroom study with 3 classes of carpenter apprentices over two days for each class. Despite its many steps, the activity proved usable and fostered many connections to the workplace, which was one of its main purposes. The teacher and the students were positive and showed high engagement in the activity. The learning gain results were mixed: the performance of the students improved from day 1 to day 2, but the learning gain measured with a pre-test/post-test mechanism did not show any significant difference compared to that of a control group.