Dragon Riders of Roar: Book 4 (Land of Roar)

Siblings Rose and Arthur adore their imaginary world of Roar, concealed within a folding camp bed in their grandad's attic. When they can't access Roar, Rose pens tales about it, creating the Dragonlands, a realm filled with fierce dragons and rumored witch clans. She crafts a school for young Dragon Riders, naturally casting herself as the top pupil. Upon reading Rose's story, Arthur feels left out, leading to a dispute that results in the story being thrust into the camp bed, where it magically comes to life. Now, Rose, Arthur, and Win must hasten to the Dragonlands, enroll at Dragon Rider Academy, and halt the calamity they've unleashed. But do they possess the skills to become Dragon Riders, and can Arthur endure a term at a school invented by his sister?