The Little Broomstick: Now adapted into an animated film by Studio Ponoc 'Mary and the Witch's Flower' book by Mary Stewart 

Mary's been exiled to her great-aunt, deep in the English countryside. Miserable and lonely, she befriends strange black cat Tib who leads her deep into the forest to an ordinary looking broomstick. Before Mary can gather her wits, the broomstick jumps into action, whisking her over the treetops, above the clouds, and to the grounds of Endor College, school of witchcraft.

But something is terribly wrong at Endor. Students are taught spells that are petty and ill-wishing, and when Mary discovers evidence of a terrible and cruel experiment in transformation, she decides to leave. But the moment her broomstick takes off, she realises that Tib the cat has been captured ...