This small-scale study investigates the relationship between gender ideology and co-ed secondary school boys' intention to participate in biology post-GCSE. Adopting a mixed-methods approach, questionnaires (n = 96) and interviews (n = 13) were carried out to collect data on the intention to participate in school science subjects, gendered perceptions of these subjects, and gender ideology from Y10 students from three Greater London co-educational (co-ed) secondary schools. The results from this study show that, contrary to numerous other studies, boys perceive biology as a gender-neutral subject, hinting at the possible shifting perceptions of school subjects with time. This could be a result of more perceived gender appropriate opportunities for boys, or the masculinisation of biology as a subject with the introduction of more technology-based topics within the curriculum. In spite of this, the perception of physics and physics-related jobs as masculine and more suitable for boys is so deeply rooted and normalised that it may deter boys from pursuing biology post-GCSE. Lastly, even though this study shows that gender ideology does not affect boys' intention to participate in biology post-GCSE, there is some evidence that gender ideology could still be a factor with subjects perceived to be gendered, like physics. Based on these findings, three recommendations are made to increase gender equity in school science education.