Six Flags Entertainment Corp. said it will reactivate a chaperone policy at its Great America amusement park in Gurnee, Illinois, starting Thursday, July 17. Visitors aged 15 and under will have to be accompanied by a parent, guardian or other adult at least 21 years old, who must show government-issued identification, stay in the park for the entire visit and remain reachable by phone. The rule will be enforced throughout the day from July 17 to July 20 and from 5 p.m. until closing time on subsequent dates. The company announced the move one week after shots were fired in the park’s parking lot, an incident that prompted heightened security but caused no reported injuries. Separately, Six Flags’ Hurricane Harbor water park in Rockford will stay closed beyond its previously scheduled reopening as crews repair damage from flooding that forced a temporary shutdown last week.