@Mame,
Thanks, Mame. This one here sounds just like the right book:
How to Spell Like a Champ. Written for ages 9 and up, How to Spell Like a Champ shows kids how to build word lists, and organize and study them most effectively. It introduces knowledge of etymology, word roots, and spelling patterns. The book is a spelling bee primer for the ten million kids who participate in Scripps Spelling Bees on the local level.
Don't forget to read the five star customer reviews.