The diverse and egalitarian nature of Estonian education has been attributed to the relatively high degree of teachers’ autonomy. Among other things, teachers are free to decide how and where to teach, and it is very common to teach in out-of-school settings such as museums, science centres, etc. The network of different learning sites that schools use has not been thoroughly described in previous literature and is thus somewhat hidden and vulnerable to rapid societal changes. Thus, this article aims to describe the practice and perceived role in formal education of on-site educators from museums, environmental centres, and other similar institutions of science and culture. Seven semi-structured focus-group interviews were carried out with 27 educators. This purposeful sample was compiled with the help of experts in the field. The limitation of this sample was that it brought together representatives of outstanding providers of curriculum-related learning activities, and so it describes the practice of excellent rather than novice or un-motivated educators. On the other hand, such a sample gives us a deeper understanding of the best practices and possibilities of the field. We found that similarly to previous results, the core practice of on-site educators involves creating, developing, and carrying out learning activities, and general organisational work. Based on the interviews, the practice of on-site educators can be described as flexible, spontaneous, collaborative, seasonal, place- and theme-specific, and project-based. Their practice is also diverse in terms of tasks both on daily/yearly basis and throughout their careers, thus illustrated by low routine and high creativity. The background of on-site educators is diverse and there are no standard career or education paths, but they can be described as strongly oriented towards constant self-development and learning, although the majority of interviewees had obtained both theoretical and pedagogical training from university and had also worked as teachers at some point in their careers. They enjoy their work and feel that it is important to connect students with nature, culture, art, or whatever their field is, to enrich their lives, support their studies, and build a better society. Thus, they often explain the value of their work through the lens of life-long learning of their students. We conclude that out-of-classroom education in the form of field trips to museums and other similar institutions is deeply connected with curriculum and helps to achieve sustainable development goals. However, as the funding for field trips has steadily increased in the past years and there are more and more schoolteachers who have no professional pedagogical training, an increasing number of schoolteachers seem to be unprepared to support students in out-of-school learning environments. We describe and expand on good practices to support schoolteachers in out-of-school learning activities and in collaboration of museum on-site educators and schoolteachers; for example, joint training programmes for in-service schoolteachers and on-site educators (especially for supporting students with special needs and content- and language-integrated learning in the context of Russian speaking students), and career changes between schools and museums (on-site educators becoming teachers and vice versa). We documented some clever funding schemes that act as boundary objects and enhance collaboration between schoolteachers and on-site educators, but we also suggest avoiding pressuring the content of learning activities through funding, as this could hinder teacher autonomy and lead to unnecessary standardisation. We suggest creating coherence between different ministries who govern schools, museums and providers of environmental learning activities, and involving on-site educators more in wider educational discussions. Education is much more than schools, and on-site educators should be considered as equals to schoolteachers when it comes to funding and decision-making about education.