Classroom orchestration refers to the teacher's (or tutor's) responsibility to identify and manage the evolving learning opportunities and constraints, in real-time. We study the use of computer technology to support this orchestration task in a multi-constraint pedagogical practice: "recitation section". In university teaching, recitation sections complement lecture sessions by providing an opportunity for students to practice the course material in teams, under the supervision of the tutors. We start by analyzing recitation sections as they are held in our university and identify the causes of their inefficiencies. We show that lack of information on the progress and the current status of the students makes the orchestration task difficult for the tutors, and on the students' side results in a hesitation to interact with their peers. Thus, we propose an ambient awareness tool that makes this information available. Our tool, called Lantern, is an interactive lamp which is placed on each group's table that shows its status, namely the specific exercise that the group is currently working on, if assistance is needed, and, if so, for how long this assistance has been needed. Several questions are raised about how Lantern can facilitate the orchestration task and increase collaboration within and between teams. To answer these questions, we describe two user studies. In the first study, we show how Lantern can help the tutors share their resources between teams, enhance students' productivity, increase collaboration among students, and improve the structure of inter-team communication. In the second study, we compare Lantern with another tool, Shelf, which provides the same information but on a single screen in front of the classroom. It appears that Shelf, instead of encouraging collaboration, creates a competitive atmosphere among students. We relate the differences between Lantern and Shelf as to how they position the displayed information in the classroom space. In a second version of Lantern, the lamps are equipped with a wireless communication module that connects them to a server. The server receives every user action and controls the lamps by specifying what should be displayed on each of them. This allows for flexibility both in terms of the variety of the learning scripts that Lantern can implement and also in terms of integration with other technologies inside and outside of the classroom. Finally, we explore the possibilities of using Lantern in other learning contexts, such as high school courses, training workshops, or open learning spaces.