While education communities have well defined commitments to protect their learners from oppressive instructional materials, discourses of science education are often left unexamined. This analysis/critique employs queer theory as a perspective to look at how one widely used textbook in Ontario schools conceptualizes notions of gender and sexuality. Results indicate the use of discourses that promote exclusively heteronormative constructions of sexuality along with sex/gender binaries. Challenging such oppressive misconceptions of sex/gender and sexuality is discussed.