The Castle in the Attic by Elizabeth Winthrop, 1985.
Ten-year-old William’s life is being turned upside down. Mrs. Phillips, his nanny, is leaving for good! Mrs. Phillips has lived with William’s family and helped to take care of William ever since he was born. Both of his parents work, so William spends most of his time with Mrs. Phillips after school. She fixes him his snacks, takes him to his gymnastics lessons, spots for him as he practices his routine, and reads stories about King Arthur with him. However, now that William is ten years old, Mrs. Phillips thinks that she would like to go live with her brother in England, which is where she is from. William is upset because he can’t imagine life without Mrs. Phillips. Mrs. Phillips tells him that he will be fine without her and that his parents will start spending more time with him after she leaves. William tries everything he can think of to get her to stay, but she is determined that it’s time for her to go.
As a leaving present, Mrs. Phillips gives him a toy castle that has been in her family for generations, along with a little lead figure known as the Silver Knight. Still, William is determined to find a way to keep Mrs. Phillips from leaving. Then, he discovers that the toy castle is magic! When the little knight comes to life and gives him a magic token that can make people small, William thinks he’s found the way he’s been looking for. With Mrs. Phillip’s impending departure and his fears of losing her, William suddenly realizes that he can use the magic coin to keep Mrs. Phillips with him. Before she can leave, he shrinks her and puts her in the castle with the knight.
Of course, turning his nanny small and keeping her inside the toy castle was unethical, as Mrs. Phillips and the knight point out, but William’s mistake proves to be only the beginning of a fantastic journey that will fulfill a legend, free the knight’s kingdom from the reign of an evil wizard, and give William the confidence he’s been looking for.
Over the drawbridge of the castle is a poem about the beginning of a quest. Mrs. Phillips had said that there was a legend about the little knight, and when he comes alive, he tells William that his name is Sir Simon and that he was turned to lead by an evil wizard who has taken over his kingdom. The poem is the key to defeating the wizard, and the little token is really only half of one that the wizard was wearing around his neck. When William turns Mrs. Phillips small, he cannot reverse the spell because he lacks the other half of the amulet. To get it, he must become small himself and fulfill the poem by crossing the drawbridge as Sir Simon’s squire. The two of them set out together to defeat the wizard and retrieve the other half of the token. Along the way, they become separated, and William must continue on to the wizard’s castle and finish the quest by himself. William has an inner strength that he doesn’t fully appreciate at first, and he can use it to defeat the evil wizard!
In the end, although William is still a little sad at saying goodbye to Mrs. Philips when she leaves, he feels a little better about her going because he knows that he can take care of himself now, thanks to his magical adventures. Mrs. Phillips tells him that he always had what he needed inside himself but that he just didn’t believe it before.
There is a sequel to this book called The Battle for the Castle.