Project LISTEN’s Reading Tutor listens to children read aloud, and helps them learn to read. Besides user satisfaction, a primary criterion for tutorial spoken dialogue agents should be educational effectiveness. In order to learn to be more effective, a spoken dialogue agent must be able to evaluate the effect of its own actions. When evaluating the effectiveness of individual actions, rather than comparing a conversational action to "nothing," an agent must compare it to reasonable alternative actions. We describe a methodology for analyzing the immediate effect of a conversational action, and some of the difficulties in doing so. We also describe some preliminary results on evaluating the effectiveness of conversational behaviors in a reading tutor that listens.