The outreach program “A scuola di Astroparticelle” was proposed in 2016 by the National Institute for Nuclear Physics (INFN - Napoli Division) in collaboration with the Physics Department “Ettore Pancini” of the Federico II University in Napoli, CNR-SPIN and CNR-ISASI Institutes. Its main goal is to engage teachers and students of High Schools in astroparticle physics projects. For the third edition (2018/19), the activities, which are also part of the Italian Educational Program PCTO - “Percorsi per le Competenze Trasversali e per l'Orientamento”, involved 18 schools for a total of 21 projects on several topics. Some projects were strictly related to astroparticles as cosmic rays, while others were more technical, as the development of particle detectors, or cross-disciplinary projects. Students worked for the entire school year and prepared materials for the final event. More than 600 students attended the event and presented their work to a jury with a poster and an oral presentation in plenary sessions. Since 2018, the program is part of OCRA - Outreach Cosmic Ray Activities - a national outreach project of INFN with the aim of collecting, within a common framework, the numerous outreach activities in cosmic-ray field carried out at the local level. The fourth edition (2019-20), in spite of the difficult situation due to the COVID-19 pandemic, has also seen the participation of 22 schools that carried out part of the activities in an online format. The project realized using the open data of the Pierre Auger Observatory will be presented in detail.