This paper explores the innovative socio-educational experience of "Huerto Alegre" (Spain), linking it to a critical perspective of Education for Sustainable Development (ESD). Going beyond the 'pluralist practices' associated with the ESD, our case study seeks to redefine ESD from a critical and ecocentric perspective within the context of the Earth Charter (EC). Huerto Alegre's social-educational programme is aimed at children and young people with the objective of creating critical thinking and fostering connections between school and the natural environment by working collaboratively with teaching professionals. The methodology of the paper focuses on a content analysis of the centre's key documents and on the narratives of students, in addition to an in-depth interview with its director. It also presents a critical reconstruction of the subject. This complements, and gives meaning to, the theoretical debates surrounding ESD -- debates that call for structural changes to our current model of society.