The paper presents the results of some evaluation research of the Eco-Schools programme in the Czech Republic. The goal was to analyse what factors correlate with pupils' action competence: their ability to deal with complex real-life situations connected with water and energy consumption in their households. The evaluation used a simple survey design conducted on a sample of pupils from the 7th–9th grades (N = 1219). The analyses showed that the level of action competence differs between boys and girls, and members and non-members of an EcoTeam. The single most important factor was pupils' perceived participation in the decision-making processes of schools.