We lay out one strand of a continuing investigation into the development of a virtual peer to help children learn to use "school English" and "school-ratified science talk". In this paper we describe a detailed analysis of a corpus of child-child language use, and report our findings on the ways children shift dialects and ways of discussing science depending on the social context and task. We discuss the implications of these results for the redesign of a virtual peer that can evoke language behaviors associated with student achievement. Furthermore, our results allow us to describe the ways in which this virtual agent can tailor its level of interaction based on a child's current aptitude in this area.