**1. Introduction**

Scholarly attention has recently been focused on the concept of action competence for sustainability and its importance to promote environmental citizenship [1]. Still, knowledge about the effects of sustainability education (SE) as an approach to foster students' environmental citizenship in terms of action competence for sustainability, where SE could be defined by holism (the approach to the sustainability content) and pluralism (the approach to teaching) [2]. The aim of this study is, therefore, to contribute new knowledge of the effects of SE on young people's self-perceived action competence for sustainability (SPACS). Through a longitudinal design, we followed students in a school where the teachers participated in a school development project aiming to implement SE. Two questions are posed:

