SPOILER: sent in by KXL who says..."This is actually a really good book, cleverly told. I would recommend reading the book instead of my spoilers."
The book takes place at St. Oswalds, a British prep school. It is told by two first-person narrators: Classics teacher Roy Straitley narrating in the present day, and "Julian Pinchbeck narrating in the present day and also telling us all about his past. There are several new teachers at St. Os that year, and he is one of them (but we arent told which, hes using a yet another pseudonym). Julian hates the school because of what happened there when he was a child. He is there now to destroy to school. Over the course of the book, Julian tells us what happened and what hes doing now to harm the school. Straitley, meanwhile, tries to figure why all these bad things are happening to the school.
Twenty years ago, Julian was the 11 year old child of the groundskeeper of St. Os. They were too poor to attend the school, so he had to attend the local state (in the U.S. public) school. But he longed to be part of that elite world. He stole a uniform and started sneaking on campus during lunch, P.E., etc. just to hang out. He chose the name "Julian Pinchbeck and befriended Leon Mitchell, a boy a couple of years older. In a short time, Julian was (secretly) in love with Leon. They share all sorts of adventures. Julian manages to keep up the charade because they are in different years. Leon falls for Francesca, a girl his age, and Julian is very jealous, but keeps hanging around because hes in love.
Meanwhile, today, students and teachers are nearly (and actually) killed, teachers are set up to look like pedophiles, a homosexual is exposed and leaves the school, and Julian secretly sends stories to the local newspaper . . . anything to discredit the school. We are led to believe that Julian is actually Keane, one of the new teachers.
The past: One night, Julian and Leon are up on a roof of St Os (Julian has copies of the keys). They talk, and what Leon says suggests that he might be bi-sexual. They touch and start to undress. Something happens. Were not sure exactly what. Leon reacts to something and calls Julian a pervert. Leon leaves. They accidentally trip an alarm. When the authorities, including young Straitley and Julians father, come, they flee. Leon slips, falls, and dies. Julian runs home. No one is sure if there really was a second boy up on the roof or not. Leons mother says it must have been Julian with him. But no one knows who "Julian Pinchbeck is. Hes not enrolled in the school.
Julian's father kills himself over the guilt of the death "of a young tresspassor on his watch." Straitley goes to talk with the groundskeepers child and mother. He asks to see the child.
And out comes . . . JULIA, the groundskeepers daughter. Yes, our narrator Julian is actually female. Not only was she pretending to be a student, she was pretending to be male. (Just like watching The Sixth Sense a second time to see if the film-makers cheated, I went back and scanned the book. So many fine details . . . Her dad never calls her anything that could be interpreted as a male or female endearment. She keeps her hair short. When her dad suggests karate lessons, we think thats silly because hes bookish, now we see its because hes a she. Julian talks about how Francesca was the competition. We thought it was gay competition; now we see better. The author brilliantly mis-directs us.). Julia says she doesnt know anyone by the name of Pinchbeck.
Present day: Julia is actually Diane Dare, one of the new (female) teachers. Straitley thinks shes in danger from Keane, and goes to see her at the Guy Fawkes Day bonfire. He slowly realizes the truth and has a heart attack, Julia fills him in on the details, (including the fact that she might have pushed Leon to his death for calling her a pervert. Its never explicitly said, but we assume that the Something on the roof was Leon seeing what Julian DIDNT have in his pants) plus the fact that Keane had nearly figured it out himself (he was doing research into St. Os past). Shes stabbed Keane to death.
Julia flees, Keane isnt quite dead yet and calls an ambulance. Julia returns to Paris, perhaps to engage in more psychopathic activities, Straitley and Keane live, and the school endures (though just barely).
The title is never explained in the book, but refers to how, in the past, members of cricket teams were either Gentleman (the were rich and played without pay) or Players (played for pay).
This book is a lot about class differences. The book has a few Latin terms which are never translated: "podex" means "arsehole."