The Clique Series by Lisi Harrison:
5 girls are forming a clique, the fashion forward and Alpha status leader being Massie Block. Claire Lyons, a middle-class girl from Florida, moves to Westchester, NY and attends a private girls day school full of snobby, spoiled teenagers. Claire's parents are friends with Massie Block's parents and the well-meaning parents try to encourage the girls towards a friendship. The girls may never be real friends but they eventually reach an understanding about each other. Along the way are plenty of mean-spirited pranks and hurt feelings.
The It Girl-
After being kicked out of a prep school for indecency and a scandal with a rock band, Jenny Humphrey decides to create a new image for herself at Waverly, an elite boarding school for rich kids. Gossip from her former life follows her all the way to Waverly, and before classes start, Jenny's already fighting against her past. Callie and Brett, Jenny's roommates and upperclassmen, are in a fight because of an incident that landed last year's third roommate--the girl Jenny replaced, Tinsley--with expulsion. After Jenny gets caught in her dorm with Callie's boyfriend, the Disciplinary Committee may have to make an example of her and expel her from Waverly. New Jenny struggles to keep her head above water when the Waverly Owls threaten to peck her eyes out. The bratty rich kids of Waverly buck their parents, their teachers, and one another to keep the drama constant and the relationships steaming. Parties and other wild events take priority over education at Waverly. Jenny likes boarding school life--it's all she's ever hoped for, so she decides to overcome her past, even if it won't go away. With a racy and surprising cheer at a school event, Jenny shows the whole student body what she's made of, and she becomes the girl of her dreams--the new Jenny--the IT girl.
The Gossip Girl series revolves around a group of six teenagers, three of them living on the sophisticated and old moneyed Upper East Side of Manhattan in New York City. They gossip, do drugs, and drink, but they also deal with sex and relationship problems. These characters attend elite private single-sex schools, where their lives are watched by an unseen character who runs a blog about them, and is always on the lookout for the scoop on everything and everyone. These characters are Blair Waldorf, Serena van der Woodsen, and Nate Archibald, as well as their scholarship student counterparts Dan Humphrey, Jenny Humphrey, and Vanessa Abrams.
The private girls' school of the series, Constance Billard School for Girls, is based on the author's alma mater, the Nightingale-Bamford School. "The school is completely based on Nightingale," von Ziegesar told ABC News. "But I exaggerated to make it more entertaining.