In a rapidly changing world, establishing strong foundations for children is vital for their well-being and resilience. Quality education is central to this endeavour and is the key to lifelong health and success. Recognizing that children thrive in the classroom when they are in good health, it is crucial to learn about health and well-being early on in primary schools. The "Building Strong Foundations" briefs, developed jointly by UNESCO and UNICEF, provide evidence-based guidance to support primary school-aged children to thrive through foundational education for health and well-being. Drawing from extensive research and consultations with leading experts from various fields and across the world, these briefs serve as a roadmap for education stakeholders to equip learners with the requisite knowledge and skills to navigate their current and future health and well-being needs. The present document is the third of four briefs. It explores how a whole-school approach to health and well-being in primary schools generates significant impacts on learners' health, well-being and education. The brief shares practical guidance and case studies to distill six essential elements for an effective whole-school approach to health and well-being.