Tobacco use is in itself a public health issue, but it also represents an identified entry point to the consumption of other toxic products. The key age group for initial consumption is that around the end of junior high school and the beginning of high school, when students' high level of autonomy is combined with a new set of educational circumstances and challenges. Intervening in a school or educational setting is not easy and often criticized. This programme involved around fifty secondary schools in the greater Paris metropolitan region, followed over several years, benefiting from substantial evaluation, including evaluation of results. The action combines a collective intervention in the classrooms coupled with the availability of a CO-testing stand to which the young people have open access. Several tools were created, including tools for evaluation. Significant preparation work and the creation and strengthening of solid partnerships were necessary, with a very strong investment in sustainability. The positive results which have been observed allow for the consideration of transfer methods for reproducing the activity combining two approaches into a repetitive and continuous process.