This chapter describes the main features of an introductory course about relativity at high-school level that focuses on relativistic dynamics. It is intended for readers who are interested in a novel approach to relativity that avoids the topic of changing reference frames, which students often find difficult. The chapter describes the basics of a course on special and general relativity. The laws of special theory of relativity, or special relativity for short, are derived from those of classical mechanics along with one extra postulate. In the Karlsruhe Physics Course , the extensive quantities, such as energy, momentum, electric charge, and entropy are introduced as basic quantities. The twin paradox plays a major role in the teaching of special relativity and is part of every textbook or course on special relativity. The development of a teaching concept for the school, in our case for the secondary school, is a balancing act.