Well, perhaps in the context of Class 5 EVS, the walls are used as a medium to tell stories. For example, if they are studying about different ecosystems, the walls could have pictures or diagrams that tell the story of how an ecosystem functions. It could also be about the history of environmental protection efforts depicted on the walls, which in turn tell stories to the students.
The phrase might imply that the walls in a Class 5 EVS setting are not just plain surfaces. They are places where stories are told. It could be through educational murals that show the life cycle of plants or animals, which are stories in themselves. It could also be that the walls display stories of local environmental heroes or events that are relevant to the EVS curriculum for Class 5 students. This way, the walls become a form of visual storytelling within the educational context.