Despite significant evidence worldwide that parents support school-based delivery of relationships and sexuality education (RSE), Australian data has generally lacked larger, nationally representative samples. Furthermore, misguided perceptions of parental attitudes are known to impact delivery. In response, online survey data were collected from 2,427 parents (56.5% female) nationwide, to examine their attitudes towards school-based RSE. Most had a child enrolled in a government school (65.3% primary, 55.7% secondary); and reported diverse religious affiliations (38.7% no religion, 21.3% Catholic, 11.1% Anglican) and voting preferences (26.7% Australian Labour Party, 25.1% Liberal/National, 23.6% undecided). Overall, 89.9% of parents supported schools to deliver RSE, with some modest differences being associated with particular demographic variables. Beyond widespread support for RSE, parents emphatically endorsed schools to address a diverse range of RSE-related issues (n = 40 topics). Parents' responses also provided insight regarding when certain topics should first be introduced and the quality of current RSE provision in schools. Findings from this descriptive overview challenge the currently overstated assumption that parents do not support RSE in schools. Such persistent and obstructive discourse is counterproductive to evidence-based strategies that seek to strengthen young people's personal and social development in a comprehensive and contemporary manner.