Only the Good Spy Young — 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 organization called the Circle of Cavan. Now, even Cammie The Chameleon can't hide. Danger has followed her to London where she discovers a trusted ally has been labeled a rogue operative. The Gallagher Girls quickly realize that the Circle's agents are closer than they'd ever feared--maybe even within Gallagher Academy's own walls. History of Espionage takes on an entirely new meaning as Cammie and her friends go looking for answers, recognizing that the key to Cammie's future may lie deep in the past.