It is a global concern that the number of students in computing-related fields has been decreasing in the last few years. As a way to improve this situation, several institutions have been implementing programs to attract and keep students in science and technology majors. This work describes a high-performance computing (HPC) course intended for secondary school students, which requires only the most basic infrastructure. In this hands-on workshop, the students learn how to assemble, install, and test a cluster. In parallel, students are exposed to a complete new area of knowledge, obtaining a more accurate view of the discipline of computer science and increasing their confidence in their ability to follow computer science. This course also provides opportunities for students to meet scientists and lose any misconceptions and negative stereotypes about science in general and computer science in particular. The aim of this paper is to detail the key concepts conveyed to students, share the course organization, materials, and examples used, and describe the overall experience.