This article examines peer-to-peer learning--in virtual schools--among the most vulnerable of students. As a description of a comprehensive case study focused on three different students with disabilities, their parents, their teachers, and their school administrators, this article examines the effects of three kinds of variables on the prevalence and quality of peer-to-peer learning among the students: these variables include 1) student aptitude for and ability to take part in peer-to-peer learning, 2) design of the virtual learning environment and its affordances for interpersonal interactions, and 3) the social and pedagogical contexts in which learning is targeted. The findings show that variation in these areas influenced whether or not peer-to-peer learning occurred.