Although engagement and learning appear linked, quantitatively measuring this relationship is challenging. New technologies offer a window into studying the interactions among classroom activity, student engagement, and positive learning outcomes in computer-equipped classrooms. A Classroom Behavioral Analysis System (CBAS) was developed to measure student engagement in a college writing class, and to test the hypothesis that an interactive lesson would increase student engagement levels in a computer-equipped classroom. Student computer-based behaviors (off-task and on-task internet visits) were compared during a traditional, lecture-based lesson (no-simulation condition) and an interactive simulation-based lesson (simulation condition). The dependent variable was student engagement as measured by the number of off-task and on-task internet activities during the lesson. Off-task internet activities were operationalized as website visits that were not part of the classroom activity; on-task internet activities included websites that related to the assigned class activity. CBAS recorded all student computer actions during the observed instructional periods. Students attending a simulation-based lesson performed more on-task internet actions, and significantly fewer off-task internet actions than did students attending a lecture-based lesson. These findings support the hypothesis that interactive lessons increase student engagement levels in computer-equipped classrooms, and demonstrate that CBAS is a promising tool for studying student engagement. (Contains 2 figures and 1 table.)