At least nine cases of COVID-19 have been discovered in the region's schools since the re-opening.
The latest case was reported on Sunday night after an individual at Ferndale Public School in St Catharines tested positive for the virus.
Prior, cases have been identified at Canadian Martyrs Catholic, Holy Cross High School, mary Ward in Niagara Falls, and at least three cases at Eastdale High School in Welland.
Niagara Region Public Health is asking the individuals who have tested positive to self-isolate.
The number of active cases in the region jumped to 77 after the weekend, which saw 38 new cases confirmed through testing.
There are now at least 77 active cases in Niagara.
