This paper presents a tool for constructing and evaluating deductive mathematical proofs using formal argumentation called CLEAR (Constructing and evaLuating dEductive mAthematical pRoofs). This tool has a twofold objective: (i) allows students to construct deductive proofs collaboratively using a structured argumentative debate; and (ii) helps instructors to evaluate these proofs and all intermediary steps in order to provide constructive feedbacks to students. This paper focuses on objective (i) and presents results of an experimental study conducted with undergraduate students. The behavior of students during the construction of deductive proofs is analyzed to show whether formal argumentation frameworks allow students to build deductive proofs and measure students’ acceptance of CLEAR.