Alan J. Pakula recalled that Liza Minnelli became very attached to him as a father-figure on the set, always asking Pakula to tell her the story's plot in child-like terms before a big scene was to be shot. He also said that Liza carried around the book by John Nichols "like a Bible" until she knew the character of Pookie Adams inside and out.
After winning the part of Pookie Adams, Liza Minnelli had a copy of the script sent over to her mother, Judy Garland, who read it and thought the part of this troubled, friendless girl would be an unattractive role for her daughter. Liza says she became defensive and argued that Pookie was a great role for any actress, but that Garland was personally concerned Liza identified too closely with Pookie.
In the original novel, the story takes place over three years. This was shortened to a single school year for the movie.