The interactional roles of smile and laughter have been widely explored in both institutional settings and mundane talk (e.g. Holt 2016; Potter and Hepburn 2010). However, the role of one specific kind of smile, what we call a 'squeezed-mouth smile' (SMS), remains unexamined. Using CA, this study explores one teacher's use of SMS in response to student turns, and how it is used to mitigate disaffiliation when treating a student response as inappropriate or transgressive. Four sample extracts out of 15-case collection are presented and analysed. The use of SMS enables her to manage a potentially delicate interactional moment by treating the student turn as inappropriate but without admonishment or discouraging further participation. Analysis also suggests, however, that SMS may be insufficient in enabling her to elicit the target response and realign interactional trajectory, allowing students to continue transgressive responses. Thus, SMS works in conjunction with verbal responses, which together identify (1) that, and why, the turn is considered inappropriate and (2) the form of the desired response. Overall, this study contributes to research on practices available to teachers in managing alignment and affiliation in classrooms.