The incident happened last Tuesday morning near 81st and May as the teen was walking to Calumet Perspectives Charter School.
Police say a man jumped out of a parked black van, forced her inside, and sexually assaulted the girl while he held her at gunpoint. A second suspect drove the van around the block.
The victim was dropped off two blocks from the school.
Parents and community leaders are calling for an increase in police presence near the school.