Peer tutoring is a simple, low-cost intervention that can be implemented in CS1/2 courses. It is hypothesized that peer tutoring helps students build a sense of community, succeed in course work, and build confidence to take further courses in the major. This paper examines the latter two hypotheses by examining the predicted and actual behavior of students in CS1/2. Course performance improvements were observed, which also strongly influence retention in computing-related courses. The measures also point to further research directions, such as social influences and the impact of peer tutoring relative to office hours or online forums.