This study examined the cognitive processes of decision making in an urban high school classroom in which tenth graders analyzed scientific evidence about current issues of technology and society. A computer program, called Convince Me (Schank, Ranney & Hoadley, 1996), provided scaffolding for making evidence-based decisions for the experimental group. During the course of instruction, both the control and experimental classes completed open-ended assessments. Student progress, in using evidence to support claims and in weighing benefits and drawbacks, was mixed. Reasons for the changes in decision making are offered.