Research into Peer Assisted Study Sessions (PASS) in Higher Education has largely focused on the positive effects of PASS on student motivation, retention and engagement. Less attention has been given to the cognitive, affective and professional development of the PASS Student Mentors through their engagement with students and academic staff. At Victoria University, learning and development for Student Mentors begins at training and continues during the semester, supported by several methods of formative feedback: weekly reflective posts through an online platform, weekly development workshops, observations, progress interviews, and evaluations. Despite ongoing training and development throughout the semester, PASS supervisors have observed that some Student Mentors do not have a clear understanding of the role expectations. This paper describes the processes undertaken to develop a rubric that clarifies PASS facilitation objectives for Student Mentors and their PASS supervisors.