Transgender and gender diverse secondary students report routine social and curricular marginalisation at school, factors which have been linked to negative social and academic outcomes. This paper examines data from the "Free2Be?" project, which surveyed 704 same-sex attracted and gender-diverse Australian teenagers (aged 14-18), to examine school gender climate as a potential stressor for the 51 (7%) students who identified as gender diverse. The paper focuses on these students' reports of their teachers' positivity regarding diverse gender expression, as a critical element of school gender climate. Multiple regression analyses revealed the significant predictive impact of teachers' positivity on gender diverse students' sense of connection to their school environment, highlighting the need for educators to be knowledgeable and affirming of gender diversity.