Prep is the story of Lee Fiora's four year experience as a student of a prestigious private boarding school in Massachusetts called Ault, an institution that for generations has educated the sons, and more recently, daughters of the East Coast's wealthiest families. It is accepted that Ault graduated go on to complete their education at Ivy League colleges. Teenage Lee is the main character in the novel and her now thirty year old self the narrator, selecting the stories and incidents that best sum up her Ault experience.
As a Freshman on a full academic scholarship, Lee is fourteen when she leaves her home in South Bend, Indiana, for Ault, which she quickly realizes is not just a different city but a different world. At her public high school in South Bend she was a star student but at Ault, Lee struggles. She is behind when she arrives and never manages to catch up with her classmates. Early in her Freshman year Lee is humiliated in Ancient History class by completing the wrong project and runs from the classroom before she starts to cry. Outside she encounters Gates Medkowski, Ault's first ever female Senior Prefect. Gates is kind to Lee which precipitates Lee's crush on her. This crush is so all-encompassing that Lee wonders if she might be attracted to women and she takes a pamphlet about sexuality and identity from the common room, hiding it in her dresser drawer.
Lee's room mate Dede Schwartz complains that someone has stolen some money from her and a couple of her friends in the dormitory including Aspeth Montgomery whose $100 bill was stolen from her bedroom during class. When Lee finds Dede going through the dresser that belongs to their other room mate Sin Jun Kim, Lee starts to believe that Dede herself might be stealing the money for attention. Despite Dede's protestations that rather than looking for money in Sin Jun's dresser she was looking for the source of the putrid odor that has recently been permeating their room. Lee is unconvinced, confiding in fellow scholarship student Little Washington, who advised Lee to tell their dormitory "mother" Madame Broussard. A few days later Lee remembers the pamphlet about sexual identity in her dresser drawer and becomes terrified that Dede will find it. Breaking a rule prohibiting students from returning to their dormitory during class Lee races back to her room, finding Little Washington coming out of another student's room furtively. Lee confronts Little who admits that she is the thief. After much soul searching Lee reports Little who is sent home immediately.
Towards the end of Freshman year the Dean announces a surprise holiday, and Lee, without a group of friends to make plans with, decides to take the bus to the mall and get her ears pierced. There are no jewelry stores at the mall but she finds a motorcycle store that sells leather jackets and biker jewelry where she is able to get her ears pierced. The sight of the piercing fun coming towards her makes her feel nauseous and after both ears are pierced Lee faints. She is rescued by a fellow Ault student called Cross Sugerman who takes her for a milkshake and makes sure she is feeling better. Realizing she is alone Cross invites her to go to the movies with his friends. Lee accepts. After the movie they notice that the last bus has already left for Ault so to avoid missing curfew Cross hails a cab and they all jump in. Cross puts his arm around Lee, his thumb massaging her neck gently, and Lee's works is forever changed from this point on as she falls into an all consuming and intense obsession with Cross.
Freshman summer Lee meets Conchita Maxwell, a gaudy dresser who is the daughter of a Texan oil tycoon. They become friendly and Lee teaches Conchita how to ride a bicycle. To thank her Conchita invites Lee to have lunch with her and her mother, as well as Conchita's friend Martha Porter. Conchita's mother sends a limousine to collect them and during the journey to her hotel Martha and Lee strike up an easy and immediate friendship, deciding to share a room the following year. When Conchita finds out about their plan she is angry and hurt, blaming Lee for stealing her best friend and immediately their friendship is over.
Lee decides to register to play the school wise game Assassin on an attempt to bring herself and Cross together. Participating players have to "kill" the student whose identity they are given by placing a sticker on them without being seen by anyone. Lee is very good at the game and enjoys brief positive attention from her peers, until Conchita, knowing that Lee wants to stay in the game, slaps a sticker onto her and assassinates her, thereby destroying Lee's plan whilst avenging the theft of Martha.
As a Sophomore Lee discovers a gift for cutting hair when talented fellow student Tullis Haskell asks her to cut off his ponytail. She is surprisingly skilled and becomes the go-to hair stylist at Ault, even cutting Aspeth Montgomery's long blonde locks. Lee's English teacher also allows Lee to cut her hair, grading the haircut rather than Lee's essay.
lee's parents pay their first visit to Ault in Sophomore year, an occasion that brings Lee extreme anxiety as she is worried that they will somehow embarrass or humiliate her with their behavior, so different to that of the other Ault parents the visit is a disaster and Lee's parents leave a day early, reinforcing the fact that although she does not fit in at Ault she no longer fits in at home either.
in the winter of Junior Year Sin Jun attempts suicide by taking an overdose of painkillers. Lee had never considered that Sin Jun might be depressed and assumes she is worried about her grades. When Lee opens the door to Sin Jun's hospital room she sees Sin Jun and her room mate Clara O'Halloran in bed together. Lee runs downstairs shocked. Later Sin Jun tells her that the relationship precipitated her suicide attempt as she had originally pressured Clara into it, and now that Clara was utterly dependent on her, Sin Jun wanted to end the relationship. Her guilt was overwhelming and suicide seemed her only escape. Sin Jun goes home to Korea for the rest of the year, returning to Ault as a Senior.
Whilst waiting for her ride back to Ault from the hospital, Lee encounters Dave Bardot, a kitchen porter at Ault who is visiting his sister in the hospital. He offers Lee a ride back to school which she reluctantly accepts when it becomes clear her ride has forgotten about her. Dave asks Lee to dinner and she accepts but their friendship does not develop as Lee is very dismissive of Dave when he talks to her in front of her friends, their reaction confirming her suspicions that a relationship with Dave would further emphasize her outsider status.
in the Spring of Junior Year Martha is nominated to be Senior Prefect. Martha is responsible and respected but definitely not one of the "in crowd" so her nomination is something of a surprise. Lee also feels it to be a small betrayal as together they were both outsiders, but with her nomination to the popular group Martha was revealed not to be such an outsider after all. Shockingly she wins the election, with Cross Sugerman winning the job of Senior Prefect alongside her. Although Lee tries not to be envious she wishes desperately it was she, not Martha, who sees Cross every day. Whilst Martha's fortunes rise, Lee's time at Ault hangs tenuously by a thread when she learns she is being considered for spring cleaning, an Ault phrase that indicates a failing student will be asked soon to leave. Lee studies harder but still cannot concentrate on anything other than Cross and trying to devise ways in which they could spend time together. Lee is given a last-chance Math paper which students complete in their rooms, signing a statement that they have completed the paper themselves, completely unaided by anyone else. Desperately trying to help her best friend remain at Ault, Martha completes the paper for Lee, making sure to include enough mistakes and wrong answers to be convincing as Lee's own work. Lee gets a passing grade on the paper and thanks to Martha is allowed to remain at Ault for Senior Year.
it is during the fifth week of Senior year that Cross Sugerman starts coming to Lee's room at night, climbing into bed with her whilst she wonders if she is hallucinating or dreaming the entire thing. The first time he visits, Martha is away for the weekend, but his second visit wakes Martha up; she wordlessly leaves the room but later tells Lee that his rule-breaking visits threaten her position at the school too, and suggests that they find somewhere else to meet. When Cross visits again Lee pulls him into the Day Girl room, which is almost never in use, and from then on their night time trysts take place there. Their relationship is secret although their best friends are aware of it. One evening the fire alarm goes off and they are almost caught, Cross running from the girls' dormitory before anyone catches sight of him. Despite their relationship Lee is devastated when Cross does not send her a rosé for Valentines, even though he sent one to Martha and several other female friends. Even though it was Lee who wanted to keep their relationship hidden she is deeply hurt at the absence of any public gestures and really yearns for her classmates to know that Cross has in some ways chosen her. Shortly before Spring Break they finally have sex, an experience they repeat on several middle of the night visits, and once in broad daylight in an empty classroom. After Speing Break, the intensity between them has dissipated. Cross visits at night just one more time, and questioning him about his absence causes a horrible, devastating argument that destroys their relationship but reveals to Lee that although she had believed Cross had no real interest in her he has actually come to know her very well.
After Spring Break Lee is called into the headmaster's office, terrified that her night-time visits from Cross have been discovered. She was worrying unnecessarily though and discovers that the New York Times are interested in writing an article about Ault, and Lee is one of the students to be interviewed. The article is intended to show that boarding schools are now very different to people's perception of them, and far from being elitist they are now inclusive and welcome students from all races and all levels of income. Lee realizes she is the token scholarship student and consequently her apprehension increases as she has never told anyone she is only able to attend Ault on a scholarship, although Martha has guessed but never mentions it to Lee. The New York Times reporter asks multiple questions about Lee's background, seeming sympathetic when learning that Lee feels like an outsider, and Lee drops her guard. When the article is printed, Lee's interview is inflammatory and seems to accuse Ault of discriminating against poorer students or those from minorities, twisting Lee's words to reinforce the boarding school stereotype. Lee quickly becomes the most despised student at the school, taking refuge in her room away from others. Martha forces her to attend all of the celebrations of Senior Week, including chapel, where Conchita Maxwell delivers an address refuting everything Lee claims in her interview. After this the hue and cry dies down and Lee is able to enjoy some aspects of graduation.
As a thirty year old Lee realizes that her Ault experiences have stayed with her far more than she had imagined as she catches herself buying a shampoo because it was the one used by the popular girls at school. Lee has remained friends with Sin Jun and become good friends with Dede. She was maid of honor at Martha's wedding but they rarely meet in person and contact between them is sporadic. She never sees Cross Sugerman again.