It happened at Roy DeShane Elementary School in Carol Stream.
The school's principal said that a student reported to their teacher that the boy made a reference to having a weapon. The school said the teacher alerted the administration and the gun was found in his backpack after a search of the student's belongings.
The gun was safely recovered and no one was hurt.
The DuPage County State's attorney said the boy's mother is a felon and cannot legally have a gun. She was charged with two counts of unlawful use or possession of a weapon by a felon and one count of misdemeanor contributing to the delinquency of a minor.
There was a meeting Wednesday night at the school to discuss the matter.