Finding Cassie Crazy (titled The Year of Secret Assignments outside of Australia and the UK) is a novel by Jaclyn Moriarty.
Cassie Aganovic, Emily Thompson and Lydia Jaackson-Oberman, attend the prestigious, private Ashbury High; Matthew Dunlop, Charlie Taylor, and Sebastian Mantegna ("Seb") attend the public and notoriously rough, Brookfield High.
He continuously threatens Cassie (i.e. "I'll break your fingers one by one"), but she responds calmly and tells no one of the abusive letters.
Lydia and Seb participate in "Secret Assignments" that eventually lead to their forming a close relationship.
By the clever use of glitter in a letter, they discover that Matthew Dunlop's true identity is Paul Wilson, the form captain and star of the school drama club.
The girls' prank is successfully pulled off and Paul realizes at the end that it was all an elaborate plan to stop him from telling the school principal.
During this time Charlie and Emily get into a fight about a prank that had been pulled off earlier in the year that had disastrous consequences for Charlie and was caused by Emily; Seb and Lydia also argue, this time about a Secret Assignment that involved discovering each other first at a cafe without knowing what the other looked like (an Assignment which Seb cheated on).
There are cruel sayings (e.g. "Brooker Bites") spray-painted on the walls of Brookfield High, each phrase followed by the Ashbury crest.
For a time, acts of vandalism are perpetrated between the schools, until a Brookfield student — whom the staff keep anonymous — incorrectly pinpoints Cassie, Emily, and Lydia as the instigators of the first attack.
In coordination with Cassie's mother (who is a lawyer), Mrs. Lilydale arranges a trial so that the girls can prove that this would be an unjust invasion of their privacy.
Emily turns the tables on the staff and proves that she, along with her classmates, has a right to privacy, and the administration agrees not to read their letters.
They are carrying evidence of the vandalism, such as the paint used to write "Brooker Bites" on the wall and the grapeseed oil that is used to smear the science laboratory floors.
Paul attempts to fight back but his guilt is clear and he has no logical explanation for Charlie, Seb and Cassie's discovery.
He runs out the door in tears and all charges are dropped against the Ashbury students as the Brookfield attacks were "inside jobs."
The story ends happily as the year wraps up with the makeup of Charlie and Emily, and Seb and Lydia.
Seb and Lydia decide to begin officially dating and Charlie and Emily show signs that they are heading in the same direction.
Lydia, an aspiring author, and Seb, a talented artist, contribute a children's book and Cassie uses words from a fake, but sweet, letter from "Matthew" as the lyrics to a song she writes and sings.
This is important to her because before her father died of cancer he told her that he thought he'd gotten sick because of the nervousness and fear he'd experienced his whole life, and had let built up.
Cassandra "Cassie" Aganovic: A shy, vulnerable girl whose father recently died of cancer.
“This energetic novel reveals the author's keen understanding of teen dynamics," says Publishers Weekly.
[2] Well-known Australian author of young adult literature, John Marsden, said in The Age, "A bravura performance .