This book constitutes the proceedings of the 12^th International Conference on Informatics in Schools: Situation, Evolution and Perspectives, ISSEP 2019, held in Larnaca, Cyprus, in November 2019. The 23 revised full papers presented were carefully reviewed and selected from 55 submissions. They are organized in topical sections named : teacher education in informatics, primary education in informatics, contemporary computer science ideas in school informatics, teaching informatics: from highschool to university levels, contests, competitions and games in informatics.