Health-related knowledge has been assumed to inform lifestyle choices for school-aged students. A "health-promoting school" provides the conceptual framework for this intervention. A large boarding school developed, implemented and refined a Nutritional Symbol System for their dining hall. The effectiveness of this social marketing strategy and school-based Health Education Program was evaluated by interviewing students ("n" = 16) for nutritional knowledge and application of the Nutritional Symbol System (NSS) to food choices in a range of contexts within (for example, in the dining hall and canteen) and beyond the school. In-depth interview data were collected, recorded and analyzed manually and via the Leximancer text mining software. Results indicated that there was a lack of consistent and accurate student knowledge derived from the Health Education Programs. Recommendations include a greater alignment between the Nutritional Symbol System, the plate and all Health Education Program materials to enhance students' health literacy round informed nutrition-related decisions.