Background and purpose: In 2020, the New Zealand Ministry of Education updated the national curriculum policy for sexuality education, broadening the focus to 'relationships and sexuality education' and strengthening guidance for both primary (Years 1-8) and secondary (Years 9-13) schools. The resulting guides detail how schools might take a 'whole school approach' to this area, including dedicated curriculum time at all levels of compulsory schooling. Methods and conclusions: This article summarises the key thinking and research that informs the latest curriculum policy update and provides justification for the content in the policy. Significant aspects include a framework based on Te Tiriti o Waitangi (The Treaty of Waitangi), Indigenous knowledges and human rights; attention to issues of bullying and inclusion; and the responsibility of schools to address gender and sexual diversity in programmes and the whole school. This background paper discusses the evidence that informs the curriculum policy update, as well as aspects of the policy context in New Zealand that precede these changes.