Characters and behaviors in the movie are based on Fey 's high school life at Upper Darby High School . It is also based on the non-fiction book Queen Bees and Wannabes by Rosalind Wiseman .
Characters and behaviors in the movie are based on Fey 's high school life at Upper Darby High School and on the non-fiction book Queen Bees and Wannabes by Rosalind Wiseman .