The Gallagher Girls series by Ally Carter

"I suppose a lot of teenage girls feel invisible sometimes, like they just disappear. Well, that's me—Cammie the Chameleon. But I'm luckier than most because, at my school, that's considered cool. I go to a school for spies."

Cammie Morgan attends the Gallagher Academy for Exceptional Young Women. Although the school  appears to be an ordinary private school it is actually a girls' school for spies. Cammie is fluent in 14 languages and can kill a  man in seven different ways. She has been taught advanced martial arts and knows about the latest chemical warfare but she definitely doesn't know how to understand boys.

Heist Society by Ally Carter

“I don't want tea, I want justice!” 

Heist Society and its sequel Uncommon Criminals by Ally Carter is a teen spy fiction. Katarina Bishop comes from a family of thieves.Kat tries to escape this life and scams herself into a boarding school where she plans to study and live a normal, honest life. This proves harder than she expected it to be. When her father is blamed for the thievery of major artworks she must be called back in action to clear his name and return the portraits to its original owners. If I say too much more it will spoil the rest of the book but lets just say that by the second book she is back in business but this time alone. She is only stealing what is already stolen, so it isn't bad is it? When she goes back to her family she must face trust issues and when she runs into trouble she starts doubting her skills.