It took me many years to find a fantasy that my struggling readers could access independently. The Dragonling, by Jackie French Koller, and its sequel, A Dragon in the Family, have been favorites. The novels are brief, but they do incorporate many of the elements of fantasy that is studied by the entire class. The chapters are short, which makes it easier for students to provide specific evidence to support their answers to the guided questions included in each reading guide.
This reading guide is also part of a larger unit I created. It includes writing prompts and an organizer for students to write their own three-scene fantasies! https://www.teacherspayteachers.com/Product/Fantasy-for-Struggling-Readers-and-Writers-3669807