In America it is rated PG-13 for violence (though I find it not that extreme) and language but here in Singapore, it is PG suitable for young, old and I definitely recommend it to watch as a family night. Overall I am very happy with this movie although it has a common story line but due to the great effect and stunts I will give 4 stars out of 5.
You can check out I Am Number Four official website to find out more.
Related Tools / Resourses:
I Am Number Four Movie Tie-in Edition (Lorien Legacies)
The Power of Six
Smallville: The Complete Ninth Season
Roswell - Seasons 1-3
I Am Number Four