Paddock Grove: Runaway Horse by J. P. Rose

Third in the friendship-led horse-riding series set at an exclusive equestrian boarding school. Welcome to Paddock Grove, a boarding school for the best, providing equestrians of tomorrow with state-of-the-art facilities and world-class tuition in everything from stable management to competitive riding. Ever since her parents sold her last horse, Tabitha has yearned for the chance to build that special bond with another. Now she finally has the chance to do this with Rusty, an ex-racehorse from her parents' training stables. Even though Rusty is a handful to ride, Tabitha isn't about to admit that she's in over her head – not if it means her parents might take Rusty away. When the Paddock Grove gang enter a competition where they must navigate a complex route across unfamiliar moorland, Tabitha is determined to not let her control over Rusty slip...