Free on-line learning promises to transform the educational landscape of the United States through a significant broadening of supplemental educational opportunities for low income and minority students who do not have access to high quality private tutoring to supplement their in school education. This research attempts to understand how to structure interactions among peer learners in online education environments using language technologies. It seeks to enhance effective participation and learning in the Virtual Math Teams (VMT) online math service, housed in the Math Forum, a major NSF-funded initiative that specifically targets inner-city, low-income minority students, and reaches over a million kids per month with its various services. This will be accomplished by designing, developing, testing, refining and deploying automated interventions to support significantly less expensive but nevertheless highly effective group facilitation. The key research goal is to experimentally learn broadly applicable principles for supporting effective collaborative problem solving by eliciting behavior that is productive for student learning in diverse groups. These principles will be used to optimize the pedagogical effectiveness of the existing VMT-Basilica environment as one example of their concrete realization. The proposed research will yield new knowledge about how characteristics of the on-line VMT environment necessitate adaptation of approaches that have proven successful in lab and classroom studies in order to achieve comparable success in this challenging environment.