Many youths have an incomplete perception of what computer science is, which leads to a lack of interest in studies on information and communication technologies. However, there is a large gap to be filled in terms of jobs in this field. It is therefore important to make young people aware of what computer science is about and of the jobs associated with it, specifically at this age as they do not yet have a precise vision of their future career. To meet this challenge, workshops have been organized to expose 12 to 15-year-olds to the basic concepts of computer science and ist subfields, such as programming, robotics, computer networking, artificial intelligence, and cybersecurity. Over three years, data were collected to measure the influence of hands-on workshops conducted in the classroom on young people’s conceptions. The workshops offered an introduction to a field of computer science poorly understood by most young people. Analysis of the data collected from more than 200 pupils across six different schools shows the important role played by both the themes addressed and the teacher’s discourse. In particular, comparisons with workshops conducted by experts highlight the problem of the lack of teacher training.