Teaching is considered one of the most trusted professions, yet literature evaluating teachers' understanding of professional behaviour is scarce. Recently, technological advancements such as Social Networking Sites (SNS; e.g. Facebook) have created fresh debate about appropriate behaviour for teachers: in school and online. The "Professional Interactions and Behaviours Scale" (PIBS) was developed to assess the degree to which teachers have developed an understanding of appropriate professional interactions with students. 30 items were developed with reference to the "Victorian Institute of Teachers Profession Code of Conduct" (2008) which states teachers are required to maintain professional relationships with students which are centered on learning at all times whether at school or not. Preservice teachers recruited for the study ("N" = 197) rated acceptability of specific student-teacher interactions and/or behaviours (e.g. "hugging a student as a form of consolation", "being friends with a student on a SNS") on a Likert scale of 1 (unacceptable) to 5 (acceptable). The dimensionality of the PIBS was evaluated using principal components analyses with varimax rotation and 20 items were retained yielding four components; befriending, hugging, external engagement and teacher disclosure. Confirmatory factor analyses were conducted and the model demonstrated adequate fit. The PIBS is a unique and promising measure for stimulating dialogue and contribute to the developing definition of "appropriate boundaries" for teachers. An appendix presents the PIBS Scale (30-item version). (Contains 2 tables and 1 figure.)