At a time of concern over the influence of social media, algorithms and artificial intelligence, this book presents a practical toolkit for secondary teacher and parents that supports secondary teachers to help their students understand the importance of critical thinking. Teenagers are facing a daily barrage of content tailored to suit their preferences and reinforce their biases. It is essential for them to understand how they can be targeted by commercial companies or entities pushing a particular agenda, as well as to recognise AI, which can manifest itself in forms such as fake news. This guide for educators and parents presents an engaging way to teach critical thinking to teenagers, combining theory with everyday issues and scenarios. It draws together neurological explanations of why teaching critical thinking to teenagers is vital and explains key critical thinking ideas through illustrations and links to video clips, featuring scenarios acted out by teenagers. The author provides diverse perspectives on critical thinking and introduces the Street Smarts model, designed to make critical thinking accessible and to embed it as a habitual skill that extends well beyond the classroom. Crucially, the book emphasises the role of dialogue in helping teenagers engage in robust conversations that focus on ideas rather than resorting to toxic or harmful personal attacks. Focusing on the crucial skill of critical thinking for teenagers, this is an indispensable resource for secondary teachers, pre-service teachers, teacher educators, parents, and other professionals working with adolescents and teenagers.