The main goal of environmental education is to improve environmental literacy, including not just more knowledge but also a better attitude toward the environment and a higher prevalence of pro-environmental behaviours. The Eco-School Program is considered the world largest environmental education program for schools, but it keeps growing without proof of its particular effectiveness in improving environmental literacy. This study compares the level of environmental literacy on Madeira Island (Portugal) among 9th grade students from Eco-Schools and ordinary schools. It applies a questionnaire with three components, addressing knowledge, attitude and behaviour toward the environment. Results show that environmental literacy among 9th grade EcoSchool students is not significantly higher than in ordinary schools. However, there are some features of environmental literacy that are slightly better in Eco-Schools, namely in knowledge, attitude and behaviours. Based on our findings, we conclude that the Eco-School Program is not really a better environmental education strategy than others strategies adopted in ordinary schools. Nevertheless, the present study fails to point out reasons for the results obtained since the design research is not adequate for this purpose.