This study aims to investigate the complexity of the practices of pedagogies of affect in physical education in response to urgent mental health issues among children and young people. As a proxy for measuring the effects of pedagogies of affect on pupils' outcomes, self-determination theory (SDT) has informed teaching approaches for student motivation and psychological wellness and, thus, it could be an indicator perspective for mental health. Previous SDT studies in physical education have shown the relationship between pupils' perceptions of need-supportive and need-thwarting teaching behaviours and affective outcomes. Nevertheless, no attempts have been made to test this teacher-pupil relationship involving observations of naturalistic teaching behaviour. Accordingly, this study examined how these observed teaching behaviours relate to pupils' affective outcomes represented by basic psychological need satisfaction and frustration, (de)motivation, positive and negative affect, and sense of coherence. Employing a cross-sectional design, this study conducted observations of one indoor lesson per class and administered a set of questionnaires to pupils. In total, 20 teachers and 381 pupils aged 11 to 15 from seven different Scottish secondary schools participated in this study. The results showed that the factor of the observed structure before the activity was significantly related to affective outcomes, while the observed controlling teaching behaviour was related to negative outcomes. Although non-significant relationships between some factors of observed teaching behaviour and pupils' variables were also found, this observational study is significant as it provides direct evidence of teacher--pupil interactions in the real-life context for developing pedagogies of affect.