Spy School (2008)

Genre: Adventure | Comedy | Crime | Family | Mystery
Starring: Forrest Landis, AnnaSophia Robb, Rider Strong

Plot: Doubting Thomas is the story of a twelve year old boy known for telling tall tales who overhears a plot to kidnap the President's daughter. When he goes public with his story, no one believes him, and he is forced to save her on his own.

http://www.imdb.com/title/tt0484831/
http://en.wikipedia.org/wiki/Spy_School