A Pony for Keeps by Jeanne Betancourt
Make friends with the Pony Pals. Anna's in trouble - she's doing badly at school and her parents think she's spending too much time with her pony, Acorn. They say that if her grades don't improve then they'll take Acorn away. The Pony Pals are devastated. Can Anna face up to her problems and ensure Acorn really is a pony for keeps?