Only the Good Spy Young by Ally Carter

When Cammie Morgan enrolled at the Gallagher Academy for Exceptional Young Women, she knew she was preparing for the dangerous life of a spy. She just didn't know that life would start during her junior year of high school. But that's exactly what happened two months ago when Cammie faced off against a mysterious organisation called the Circle of Cavan. Now even Cammie 'The Chameleon' can't hide. Danger has followed her to London where she discovers one of her most trusted allies has been labelled a double agent. The Gallagher Girls quickly realise that the Circle's agents are closer than they'd feared -- maybe even within the Gallagher Academy's own walls. Cammie and her roomates must call upon old friends if they want to find the traitor at their beloved school before it's too late...Special 10th anniversary edition, including an exclusive new epilogue.

ISBN: 9780734417251