OBJECTIVE: The purpose of this article is to describe a public school-based educational intervention (EI) designed to increase knowledge, improve attitudes, and change practices related to road safety. METHODS: We used a mixed-methods evaluation of a road traffic safety baseline diagnosis conducted in 4 public schools, 2 primary and 2 secondary. Research was organized into 4 phases: (1) diagnosis, (2) EI design, (3) implementation, and (4) evaluation. We used convenience sampling (n = 219 students) across schools and applied a pre-/posttest design based on quantitative and qualitative data. The former related to surveys on road safety experiences, knowledge, attitudes, and practice and the latter to observation checklists, community mapping, ethnography, and focus groups. To compare pre-post scores, we used multilevel mixed-effect ordinal logistic regressions. We developed data matrices, field notes, and systematized community mapping. We also transcribed focus group discussions, generated categories, and carried out thematic analysis. RESULTS: Ethnography indicated poor sidewalk conditions, no helmet or seat belt use, overcrowded public transportation, and no traffic lights or proper signals. Pedestrians did not use sidewalks and crossed streets unsafely. Subsequent to the intervention, however, the study population showed significant changes in their knowledge, practices, and attitudes. They identified road traffic incidents (RTIs) as the first cause of death among children and youth, and most understood that the solution to the problem was incumbent upon each and every individual. They also displayed increased perceptions of danger in practices such as traveling on overcrowded public transportation, failing to wear seat belts in cars and helmets on motorcycles, crossing the street while using mobile phones or playing with friends, and riding with drunk drivers. Changes varied according to gender, and students reported being able to carry out safe practices only when they were in control of the situation; for instance, as pedestrians. CONCLUSIONS: Because safe practices depend not only on children and youth but on the adults and social environment surrounding them, it is essential to engage parents, teachers, and decision makers in efforts to reduce RTIs. This will improve the establishment of commitments to impact social reality through consistent changes and mobilize greater resources for creating more secure communities in matters of road safety.