Gifted: Now You See Me by Marilyn Kaye

The Gifted class are getting suspicious that there's a spy in their midst. But who? The chief suspect is queen-of-mean Amanda, who's started acting out of character and volunteering in the school office. Tracey and Jenna join forces - and gifts - to try to find out more. But when mind-reader Jenna is framed for a crime she didn't commit and sent to an institution, Tracey is on her own. Using her ability to become invisible, Tracey searches for answers and finds out more than she bargained for . . .