This book goes beyond the surface-level 'just say no' approach, offering deep insights into the real reasons young people may turn to harmful substances and exploring the complex factors – such as coping with trauma, mental health struggles or feelings of inadequacy – that influence these decisions. Timely and relevant for all educators teaching Personal, Social, Health, Economics (PSHE) education in secondary school, the book provides practical teaching tips, safeguarding guidance and strategies for creating a supportive and inclusive classroom, as well as informative and engaging lesson plans that empower students to make healthier and more informed choices. Supporting a spiral curriculum, it integrates subjects including mental health, science, English and maths, offering a holistic, interdisciplinary approach to learning about harmful substances. This book is not just about prevention teaching – it's about creating a lasting, positive impact on young lives that they can carry on into adulthood. Created to support all teachers, particularly those new to the subject or who are non-specialists, Harmful Substances provides crucial information and knowledge that will ensure effective and impactful classroom sessions.