One of Heinlein's juveniles. Though you've got to notice that it starts with a college course that has a final of being dropped on some planet -- and surviving. And bright kids can take it in high school.
Rod Walker just learned with the rest of his class that it's the next day. Sees some of his world, filling us in, and has some conflict with his family, but ends up going. His military sister talks him out of a gun but gives him an additional knife.
When he arrives -- the title tunnel in the sky refers to the transportation means -- his first sight of another candidate is the corpse of a classmate, whose missing gun clearly reveals he was murdered. He faces thereafter a night chorus of wailing beasts, someone found in a tree and injured, trying to take shelter in a cave, a wild guess that they are still on Earth, the discovery of a serious problem that has the candidates having to band together, elections, and much more.
