The teen has been charged with unlawful use of a weapon -- possession/carrying/concealing a weapon, Chicago police said.
CPD previously said a weapon was recovered in the 200-block of South Laflin Street in the West Loop just before 8:15 a.m. Monday. No one was injured, and one person was taken into custody.
School officials said the gun was found during a "standard entry screening," and did not get any farther into the building.
There does not appear to be a threat to the school community, CPS officials said.
CPS said it would handle the matter in accordance with school policies.