Cosmic rays are a unique tool for introducing high-school students to particle physics concepts and methods; their detection and study, with a variety of cosmic ray experiments in schools, is an excellent way to acquaint them with the world of scientific research, motivate and inspire them. Cosmic-ray experiments in schools, using a variety of detector types and sizes, exist in many countries, often as part of networks, and in some cases they also produce scientific results. In order to better exploit the great potential of cosmic-ray experiments for particle physics outreach, IPPOG, the International Particle Physics Outreach Group, started an effort to put such experiments under a common umbrella; a workshop was organised in Rome in 2017 where a whole spectrum of cosmic-ray related activities in schools were represented. Global cosmics – a working group of IPPOG – follows up and reports during IPPOG meetings. Activities such as International Cosmic Day, organised by DESY and Cosmic Ray Week, organized by Quarknet are promoted and strongly encouraged by IPPOG.