I was read this short story on a school field trip in 6th grade or so, so it is probably from the 70s or 80s, but never knew the title or author.
It's about a boy who slowly discovers that he is in fact the animal in an alien zoo.
I'm fairly sure what leads him to the discovery is the realization that the only way the moving sidewalks in his world, which are motionless until he steps on them, could only work if he is the only one using them.
Thanks!