Out-of-school environments offer a unique opportunity for experiental learning which transcends the role of educational resources and teachers. This article introduces the special topic of out-of-school learning in science and mathematics education. First, we present the theoretical underpinnings from the movement towards crossing the boundaries of school in educational practices and broadening educational spaces. We continue with the key facets of out-of-school learning through a constructivist approach, aided by the concept of mediation environments as the third educator from a socio-material perspective. Furthermore, we focus our discussion on a selection of articles from this special number as an international overview on out-of-school learning. In the conclusion section, we discuss the gaps that the following works fill, as well as new questions that arise in the area. The closing remarks highlight the promotion of active learning in students, considering the role of the environment as the third educator.