Judy Abbot is the main character. She's a red-headed orphan much alike Anne Shirley of the Green Gables books. She receives a scholarship from a mysterious "Mister John Smith" whom, upon glimpsing his shadow, she dubs Daddy Long Legs.
She then gets the chance to attend high school (rare for orphans since it was not publicly sponsored in older times) and makes friends, though she has trouble fitting in due to her lack of wealth.
Here are pictures of Judy from when she was younger, seen in the ending credits: