Recent years have witnessed growing acceptance of gender and sexuality diversity in Australia; yet, its inclusion in the school curriculum remains contentious. Despite evidence to the contrary, there is a commonly held belief that parents consider the inclusion of such topics inappropriate. In the light of this, this paper focuses on an analysis of three qualitative items from an Australian national survey of parents of children attending government-funded schools. Informed by the responses to these questions, we sought to better understand the concept of age-appropriateness present in the discourses deployed by a (minority) number of Australian parents who did not support gender and sexuality diversity-inclusivity in the curriculum. Thematic data analysis identified three key themes used by parents to warrant gender and sexuality diversity curriculum exclusion based on age inappropriateness: namely, inclusion is 'confusing'; children are too 'immature'; and children are too 'easily influenced'.