The Einstein-First project aims to change the paradigm of school science teaching through the
introduction of modern Einsteinian concepts of space and time, gravity and quanta at an early age.
These concepts are rarely taught to school students despite their central importance to modern
science and technology. The key to implementing the Einstein-First curriculum is the development of
appropriate models and analogies. This paper is the first part of a three-paper series. It presents
the conceptual foundation of our approach, based on simple physical models and analogies, followed
by a detailed description of the models and analogies used to teach concepts of general and special
relativity. Two accompanying papers address the teaching of quantum physics (Part 2) and research
outcomes (Part 3).