Background: Teacher-student relationships have been linked to various aspects of students' school functioning, including social-emotional well-being in school, but the underlying mechanisms need more investigation. Aims: In this study, we analysed longitudinal data to test if students' classroom behavioural engagement was a potential mechanism of change that explained how teacher-student relationships affect student school satisfaction. Sample: We used an archival dataset with a sample of seventh graders (ages 11-14, M[subscript age] = 12.7 year) in a middle school in the Southeastern United States. Methods: Adolescents completed self-report surveys across three waves over the course of 18 months. Results: Longitudinal structural equation modelling analyses revealed that teacher-student relationships were positively associated with positive classroom engagement behaviours and school satisfaction, respectively, at each time, and positive classroom behaviours at Time 2 fully mediated the longitudinal association between teacher-student relationships (Time 1) and school satisfaction (Time 3). Conclusions: Taken together, results suggested that fostering positive teacher-student relationships to increase students' positive classroom behaviours could be an effective pathway to promote students' satisfaction with school. The applications of the results in educators' and psychologists' work, such as consultation and trainings with teachers, are discussed.