To prevail in modern, asymmetric conflicts, most warfighters must socially engage with people of diverse cultures to accomplish a variety of military missions. In spite of this pervasive need, no scalable solution exists for training social skills. Live role-playing is prohibitively expensive and dynamic social skills cannot be learned using traditional, virtual environment based training architectures that rely on carefully scripted scenarios and statically animated, synthetic characters. This paper offers a possible solution for social training by describing an exploitation of Expressive Artificial Intelligence (AI) and an adaptation of cognitive apprenticeship to create a synthetic, mentored, social practice environment. Expressive AI views AI as an expressive medium, and aims at the algorithmic and architectural research necessary to create highly interactive and generative experiences. To allow for true social interaction, our team focused on creating combinable chunks of behavior that enable synthetic characters to participate in a wide variety of jointly meaningful social activities with each other and with a human learner. To meet the challenge of mentoring in this environment, our team borrowed from the deep teaching method of cognitive apprenticeship, exploiting techniques such modeling and scaffolding. To this mix was added real time coaching using the same social simulation mechanisms that create the synthetic characters in the simulated world. A demonstration version of the system was developed under the Defense Advanced Research Projects Agency (DARPA) Strategic Social Interaction Modules (SSIM) program, which in part is designed to illustrate training of general social competence in unfamiliar contexts rather than culture-specific knowledge and skills, using computer controlled characters and instruction in synthetic environments. This work on the design and engineering trade-offs and innovations in simulation control structure should spark interesting debate in the education and simulation communities as well as serving as the basis for others heading in this same direction.