Now onto Galax-Arena by Gillian Rubinstein:
Before The Hunger Games—even before Battle Royale—there was the Galax-Arena, where children are pitted against each other for the benefit of a shadowy audience that feeds on their fear. A Children's Book Council of Australia Honour Book for Older Readers, Galax-Arena is a dark, uncompromising thriller and a cult classic.
Joella, her brother Peter and her sister Liane, are kidnapped and transported to become entertainers for an alien species. Many of the performing children are desaparecidos—the disappeared—kidnapped from third world slums and chosen for their extraordinary gymnastic ability. For the children, there is only one escape from the Galax-Arena: out of the door and into death.