Cross my heart and hope to spy. Ally Carter. 2008.

Cammie Morgan may be a spy-in-training with a genius IQ, but there are still a lot of things she doesn’t know. Like, does her ex-boyfriend even remember she exists? And why is her mother acting so strangely?

Despite Cammie’s best intentions to be a normal student, danger seems to follow her. She and her friends learn that their school is going to play host to some mysterious guests - code name: Blackthorne. Then she’s blamed for a security breach that leaves the school’s top secret status at risk.

Soon Cammie and her friends are crawling through walls and surveillance the school to learn the truth about Blackthorne and clear Cammie’s name. But this time the targets are toughern(and hotter), and the stakes for Cammie’s heart - and her beloved school - are higher than ever.