Heterosexism and heteronormativity are pervasive in the South African society, but to what degree are they present in Life Orientation (LO) textbooks? This question, explored through a content analysis of widely used Grade 10 LO textbooks, was framed by queer theory. The paper quantitatively examines the coverage of sexualities, and qualitatively examines how sexualities are constructed and projected in the texts. The quantitative analysis reveals a low percentage of statements devoted to sexuality overall and the normalisation of heterosexuality mainly through the exclusion of lesbian, gay, bisexual and transgender (LGBT) sexualities but also through techniques of differentiation, hierarchisation and homogenisation. The qualitative analysis reveals inadequate information about sexualities and in its place a simplistic, moralistic ideological approach. Furthermore, discussions of the family, dating, safe sex and marriage assume heterosexuality as the norm. Nineteen years after the democratisation of South Africa and 17 years after the ratification of South Africa's constitution which explicitly forbids discrimination on the basis of sexual orientation, LGBT sexualities are largely invisible in school LO curricula. Since this is a subject that is compulsory for all learners and its express aim is to prepare young South Africans for participation as citizens in a just and democratic society, the absence of LGBT issues and identities helps perpetuate prejudice and violence towards LGBT communities.