The success of school-based mental health interventions is often inconsistent, in part due to lack of input from teachers and students in the programme design. Therefore, the involvement and engagement of teachers in the co-production of an intervention, especially within data analysis can create more innovative and effective solutions. This paper presents a teacher-led qualitative data analysis using a new approach within the field, participation theme elicitation. This approach will be used to gather information relevant to the initial development of a school-based mental health intervention. Teachers identified the following themes: (1) Physical activity as a stress reliever, (2) Programme facilitation, (3) Exam pressure and (4) Solutions to improve negative mental health. Results from the teacher-led analysis are broadly similar to previous research in the field. Our findings demonstrate that teachers can have a valuable input into research findings which should help address the development of a school-based mental health intervention. In summary, the findings suggest that the use of participatory theme elicitation is a valid and effective method to address the gaps and limitations of participatory qualitative data analysis.