Currently, all members of the educational community have a relevant role in the development of professional competences on the sustainability of students. This is supported by the findings obtained by different research studies carried out in different countries and which show the need to characterize and evaluate the practice of EGS as key agents in the training and counseling of teachers on sustainability topics, which, in turn, is the goal of this study. To address this, we have conducted an exploratory study based on the case study of EGS members in the metropolitan area of Granada (Spain) that has helped us to profile the professional practice of its members in the development of professional competences in Education for Sustainable Development (ESD). Answers to a questionnaire provided by 43 teachers who are linked to the EGS have been investigated in addition to an interview to six formal members of the EGS. Results evidence that transmit some values over others correlates positively with the type of competences for sustainability that they promote. Therefore, this shows the interrelation of these competencies with the teaching-learning process and, consequently, with the promotion of an education for sustainability. We conclude that counseling on participatory methodologies, working on values, competences, and curricular sustainability, as well as the cross-curricular nature of the content that is imparted, are the most effective ways from which these teacher guidance services can promote the development of professional competences linked to sustainability in schools.