School-based nutrition education (NE) has an important role in promoting healthy eating habits and helping prevent chronic diseases--particularly among disadvantaged children and youth who are more likely to experience poor diet quality. However, teachers report being underprepared or time-poor in delivering NE and there is a growing trend for schools to outsource health-related content to external providers. This study evaluated the effect of an experiential NE session on Years 3-12 students (N = 1,714) and teachers (N = 178), developed and facilitated by a hunger relief charity for low socioeconomic schools that access a school breakfast program. The results showed significant increases (p < 0.001) in student knowledge and attitudes towards healthy eating. Teachers indicated they improved their knowledge of how to teach children about healthy eating and were motivated to include more NE in their teaching programs. The study shows that targeted, experiential NE sessions delivered by external experts can improve students' knowledge and attitudes toward healthy eating post-intervention and may reduce barriers to the provision of ongoing teacher-led NE. The opportunities for sustained impact in the context of a school breakfast program are discussed.