Three and a half stars. Pretty good.
Will Stronghold is the son of Steve and Josie Stronghold--also known as The Commander and Jetstream, the world's top superheroes. "Sky High" is the school where superheroes (and sidekicks) are trained, and Will's parents were both star pupils there. They have high hopes for Will to join them in the family business (i.e. saving the world), but out of embarrassment Will hasn't told them that he doesn't actually have any powers yet.
The film blends two genres very successfully: the superhero film, and the (American) high school experience movie. There is a villain in the piece, but she only plays a major role as such in the last twenty minutes or so. The bulk of the film is about Will discovering who his friends are, and learning more about who he is. It's less like The Incredibles and more like Buffy. In fact, it would make a great TV series. Especially if they could keep hold of Bruce Campbell and Kevin McDonald, who both give tremedous cameo performances as Coach Boomer ("Sonic Boom") and Mr. Medulla.