In this paper we introduce an original scientific and educational experience conducted with Italian 16/17 years-old students attending Scientific Lyceum "Mangino" of Pagani (Italy). It was inserted in an Italian Educational Program PCTO (i.e. Percorsi per le Competenze Trasversali e per l'Orientamento), active in High Schools on a national level, with the aim to make students consolidate and expand the curricular content’s knowledge via internships in private or public working environments. For this specific item, concerned CTA-PCTO (Cherenkov Telescope Array-PCTO), the students, led by a teacher and an INFN researcher, venture out into the innovative technology and the future scientific achievements of CTA, which will be the first ground-based gamma-ray observatory and the world’s most sensitive and powerful gamma-ray instrument. All the activities carried out during the CTA-PCTO were organized as an action-research to develop an alternative, effective, and motivating approach to the study of astroparticle physics, and in particular of gamma-ray physics. In this way students benefited to the scientific and technology information of CTA and its telescopes, and they were engaged in producing different didactic items, also useful to introduce CTA technologies to other students. They created a paper model of the CTA's Large-Sized Telescope (LST), realized a crossword puzzle and write an article, and finally, they presented their work to the general public during the "European Researchers' Night" in November 2020. The mere need to report their results has produced remarkable results in their ability to write and communicate on scientific items.