Insects are increasingly used in environmental education (EE) due to their high diversity, ecological relevance, and presence in urban environments. This study evaluates the use of insects as a pedagogical tool by implementing formal and non-formal EE activities with secondary students living in areas with a high incidence of vector-borne diseases, on the coast of Oaxaca, Mexico. A total of 118 students participated in theoretical, fieldwork, and laboratory activities, as well as a public outreach event (“Entomo-Expo”). Pre- and post-workshop questionnaires were used to assess changes in knowledge, perceptions, and attitudes. At the end of the workshop, students identified 11 insect orders. They communicated their knowledge using scientific terminology, and negative reactions toward insects decreased, particularly in reports on killing behaviour, while responses associated with observation and the release of insects increased. Participants also recognised key ecological roles of insects, especially pollination. These results are associated with improvements in students’ conceptual understanding and more positive attitudes towards insects following participation in the programme. However, given the pre–post-design without a control group, these findings should be interpreted as changes over time rather than causal effects. To address the persistence of negative behaviours in older students, EE should employ both formal and non-formal teaching strategies to support a sense of responsibility and encourage a cognitive shift toward sustainable development.