Computer tools for learning are often thought of as providing practice in working with symbolic representations. We exemplify a different perspective in which the technology augments the kinds of learning conversations that can take place. Research from the Optics Dynagrams Project illustrates contributions from this perspective. I will describe pre-intervention learning environment characteristics and student learning, our design strategy for new activities and technologies to address problems we observed, and results with a classroom field test of our redesigned learning environment. In the Dynagrams learning environment, small groups of students work with a software simulation of phenomena of geometrical optics. They observe optical situations in the world or laboratory, use dynamic diagramming tools to make predictions and arguments to justify them based on scientific principles, definitions, or prior experiences, and test these predictions in runs of their simulation models. The dynamic diagrams become symbolic vehicles for externalizing student cognitions for peers and teacher, as well as the topic for negotiating group and individual understanding toward physics norms. The pedagogical goal is to have students become better able to engage in appropriate conversations about the conceptual content they are investigating. Such inquiry-focused discourse is a fundamental part of learning environments in authentic practices outside schools; our aim is to examine ways for augmenting such learning conversations in schools.