Introduction: Tooth decay is the most common reason for non-emergency hospital admissions in 5-9 year olds. As such, it is included in the England school curriculum at 8-9 years to facilitate improved oral hygiene and prevent tooth decay. Aim: Measure student and teacher baseline oral hygiene knowledge; determine effect of the e-Bug oral hygiene lesson on student knowledge; explore teacher views on the lesson. Methods: Mixed methods evaluation. Baseline student and teacher knowledge questionnaires. Intervention classes received the e-Bug lesson. Post-intervention student questionnaires and semi-structured teacher focus groups. Results: 121 students completed baseline questionnaire -- results indicate high knowledge about which foods/drinks are bad for teeth; low knowledge about tooth decay and appropriate tooth brushing behaviours; confusion over what foods and drinks contained sugar. 58 students received the intervention; 10 out of 17 questions in lessons showed significant increase in correct responses (p < 0.05). No significant improvements reported in the control. Overall teachers were very positive about the lesson and suggested some improvements. Conclusion: Children have gaps in oral hygiene knowledge. Teachers acknowledge oral hygiene as a priority which should be taught more frequently, citing e-Bug as a valuable oral hygiene educational resource. Curriculum leaders should be encouraged to increase oral hygiene education using a whole school approach.