Collaborative decision-making is one of the emphasized student skills required by educators from different domains including science, technology and society. Multi-surface environments (MSE) appear particularly well suited for such learning activities, with large shared surfaces dedicated to the overview of information and context awareness, while personal surfaces serve browsing and analytical purposes. In this study, we present the design of Pickit, a MSE tool supporting collaborative decision-making activities. We show how Pickit is used by four groups of high school students as part of a learning activity. We analyze students' interactions with digital devices that are related to given phases of the decision making process. Our results show that MSE are particularly interesting for such learning activities as they enable to balance personal and group work. The introduction of personal devices (tablets) makes free riding more difficult, while enabling development of personal judgment. By using Pickit, students successfully made their decisions and meanwhile better knew about the decision-making process.