What metaphors are used in The Replacement by Alain Robbe-Grillet?

The story of the schoolboy and the tree works as a metaphor for indeterminacy. When Robbe-Grillet weaves this plot into the others, he declines to show readers any temporal or spatial links between them. The teacher could be watching the schoolboy out of the window to alleviate his frustration over his students' inability to properly read and understand the story, or the schoolboy could be a memory or an imaginative creation for the teacher or for the students. At one point, the narrator notes that the students cannot see out the frosted windows. Perhaps the schoolboy is their imaginative rendition of what is on the other side.