I am trying to find a book. I don't know the title or the author. Its fiction and the story was roughly about a father who was a caretaker at a posh boys school. His child went to a local school but decided to infiltrate the posh boys school, started attending and befriends one of the pupils there.
About halfway through the book the reader makes the shocking discovery that the child of the caretaker is actually a girl. Up until this point the reader makes the assumption its a boy.
It is the sort of psychological thriller that Ruth Rendell might write. Any help in identifying it would be appreciated. I need it for a book club. Many thanks.