The boy was with his mother as they were entering the school about 9 a.m., the Chicago Tribune reported. He refused to place his book bag into an X-ray machine, police said. When he refused a second time, he tried to give the bag to his mother, but she refused to take it.
Security officers then searched the bag and found an unloaded .25 caliber semiautomatic handgun, the newspaper said.
The boy was arrested and charged as an adult with unlawful use of a weapon in a school zone. He was ordered to appear in court Tuesday.
His mother was not charged.