Everything you need to understand or teach The Only Ones by Aaron Starmer.
Presenting a dystopian vision of the future with a sci-fi twist, Aaron Starmer's The Only Ones is a fantastical account of a group of kids that find each other and come together after the vast majority of the people on Earth mysteriously vanish. Martin Maple is the driving force, coming from his solitary existence on an island to the society of Xibalba where he tries to rally the children there to figure out where everyone went. Starmer tackles, among other things, themes of loneliness, love, and time travel.