Parents were informed about the potential for exposure on Monday.
Chicago Public Schools officials confirmed there are 13 cases of COVID-19 at Coonley. The school has had 40 cases in the month of March.
Coonley has a high vaccination rate with 91 percent of students having received at least one dose. Eighty-nine percent are fully vaccinated.
The school has 870 students and the on-site voluntary testing has been increased.
The Chicago Teachers Union had concerns that COVID transmission would increase after CPS went mask optional.