The combination of classroom voting system (clicker) questions and peer instruction has been shown to increase student learning. While implementations in large lectures have been around for a while, mathematics has been increasingly using clickers in classes of a smaller size. In Fall 2008, I conducted an experiment to measure the effect of clickers on exam performance. The experiment was conducted with two sections of Calculus 1, using the same examples either on the board or with clickers. By comparing only the lower-performing students in the sections and alternating use of the clicker between sections, I was able to obtain modestly significant results showing improved exam performance for low-performing students, despite a small sample size. (Contains 4 figures and 6 tables.)