Easy one coming up.
A horrific world in which preteen children are encouraged to leave home and set out into the wild to hunt down and and subjugate innocent creatures many of which are massive in size with absolutely lethal abilities that could easily kill the children. These animals are then kept in extremely confined quarters often much smaller than the creatures themselves. They are then forced to gladiatorial battle against creatures caught by other children and adults in no holds barred duels until one or the other is knocked out, these poor animals are then revived to fight over and over in the name of "training" all for the entertainment of these children and other observers.
What's more these poor little guys are often enslaved to do the humans bidding, hauling construction equipment and materials, mining, providing power... They are not paid for this service and have little to no rights even though many of them show signs of higher intelligence. especially given that from the age of 10 most of these children do not seem to be in any kind of formal education.