As global challenges to sustainable development are increasing, there is a growing pressure for educational systems to embed education for sustainable development (ESD) into formal education. To meet this demand, Eco-School systems were established in many countries during the past decades. Using General Inductive Approach to analyze raw data sources like interviews with experts and eco-school principals, documents, and official as well as educational research databases both in Hungary and in Israel, the paper compares the process and the outcome of the implementation of eco-school movement in Hungary and Israel. The major conclusion is that eco-school system itself has a significant positive but limited effect on the implementation of ESD in educational systems. Without a person, a "change agent," without the commitment of the principal or the teachers, the central eco-school initiative could not trigger changes on local levels; however, eco-school systems may survive for another decade if eco-school teachers continue innovation and collective learning. On the system level, the existence of the movement demonstrates the sustainability pedagogy for decision-makers -- and therefore they can be satisfied without further efforts.