Ballet Shoes by Noel Streatfeild
In this book, we meet Pauline, Petrova, and Posy, three orphans who have been adopted by Great Uncle Matthew and placed under the care of his great niece, Sylvia. The girls decide on the last name of Fossil for themselves, since that is what Great Uncle Matthew collected. Unfortunately, Great Uncle Matthew, or GUM as he was known by the girls, left on another expedition and was gone so long that the money he left began to run out. How was Sylvia going to find the money to keep the house and the girls? How was their education to be paid for? The answers can be found in this charming story about three orphan girls growing up and finding their way in the world.