Ethics approval and consent to participate
All methods were carried out in accordance with relevant guidelines and regulations. The trial received full ethical approval by Swansea University Ethical Committee on 29/10/2019 (Reference number: 2018–0272–259). The Guide Cymru is being adopted as part of the National Curriculum of Personal Social Education (PSE) in schools in Wales and is therefore delivered to all children within the year group at the school at the teachers’ discretion, without the need for consent from parents/caregivers. Informed consent from participants was waived by the Swansea University Ethical Committee. This was on the basis that the intervention programme was being delivered as part of the National Curriculum and was being delivered within schools alongside other lessons within the learning curriculum. Parents were informed by each school that the Mental Health Literacy programme was being delivered as part of the curriculum and were given the opportunity to withdraw their child from these lessons if they wished. Completed questionnaires contained no personal information to preserve anonymity.