I read a book in the 5th or 6th grade ('90-91) that has always stuck with me, but I can’t recall the title or any of the characters names.
The plot was about a pre-industrial world populated by humans and some type of humanoid creatures that were hunted for sport, or kept as pets. Some could speak the human language, but it was dismissed as parroting rather than communication. As the book moves on, we find out that this is some sort of forgotten colony world that had dabbled in human/animal genetic manipulation which resulted in these creatures. One of the characters is an undercover operative from the planetary empire and is there to determine if this world is ready to be reintegrated. He befriends one of the humanoids and goes on a berserk rampage when this creature is killed.
Sound familiar?