Food for Thought (and maybe worms): Mary Amato.The Word Eater. New York: Holiday House, 2000.
Mary Amato demonstrates how to turn fantasy into science fiction.
There are threestories here: Fib, the worm rejected because he can't eat dirt, Lerner Chanse, a new girl in school who doesn't want to end up in the out group (SLUGs) but isn't too keen in the in-group (MPOOE) either and Lucia, a Bellitan child forced into factory labour.
When Lerner finds Fib she discovers that he eats words. If he eats a word, its referent disappears. This could be a wish fulfillment fantasy, but Lerner isn't that kind of child. Instead, she embarks on an experiment in which she records on paper what she has asked Fib to eat, and what the consquences were. With this she learns to be very, very specific--to become sensitive to the fact that single words are not phrases, and that accurate description is important. But Lerner does change the world: she frees Bobby Nitz from his bullying father by having Fib eat "Mr. Nitzes' meanness". She gets rid of Attackaterriers (dogs trained to be vicious by having thumbtacks pushed into their paws) by getting Fib to eat the first part of the word. As a consequence which she never sees* Lucia is liberated, the dogs having become quite cute.
Towards the end the leader of the MPOOE, Reba, gets hold of Fib and tries to get him to erase the school, so teaching us all a lesson about irresponsibility. Lerner gets Fib back and instead erases her teacher's trousers, so he is embarrassed enough to leave profession in which he has little interest. Finally, Fib asks to have his magic erased and Lerner arranges it.
The book is moralistic but stays interesting and fun because it isn't about morality per se, pr not morality as an absolute, but morality as something that has to be continously thought about and reconsidered. The book won a stack of awards and deserves them all. I liked it because the nerd gets all the prizes by showing how nerdiness is a valuable attribute.
*it is this kind of consequence which is missing from most children's sf.