Comprehensive sexuality education (CSE) is promoted around the world to improve young people's sexual and reproductive health and rights, and to address gender-based violence. Teachers play crucial roles in enacting CSE, yet only few studies have placed them centrally to understand CSE re-contextualisation in schools. Hence, drawing on interviews, focus group discussions, and classroom observations with 56 participants, this paper presents how CSE teachers enact CSE policy and which factors affect their enactments at schools in Ethiopia. The paper highlights that while CSE teachers were typically conceptualised as 'facilitators' of the CSE initiative presented here, in practice teachers seemed to perform what might be understood as 'activist' roles within and beyond the classroom and school. Despite this activism, teachers' possibilities to address gender-based violence still seemed limited, in part due to lack of guidance from policy and programme designers, lack of support from community and school management, and socio-economic factors.