KITCHENER -- Five-year-old Olivia Ristovski made it through a week of kindergarten before COVID-19 interrupted her classes.

Her mother, Chantele, said that on Wednesday, her daughter was sent home with a letter from her Catholic elementary school in Cambridge, Ont., that notified the family that one of Olivia's classmates had tested positive for COVID-19.

One week into her daughter's school year at St. Anne Catholic Elementary School, it came as a shock to Ritovski.

"It's something you think is not going to happen and in reality it's going to, and it has," she said.

In a statement, public health officials said that the entire class has been asked to self-isolate and get tested.

The family's experience is unfortunately not a unique one. Millions of Ontario students returned to school this month, and as of Thursday afternoon, 51 schools had reported a combined 62 cases of COVID-19. Of those, 20 have been identified in students and 22 have been identified in staff.

The other cases are in individuals who have not been publicly identified to protect their privacy.

One school—Fellowes High School in Pembroke, Ont.—was ordered to close after three staff members tested positive for COVID-19 since last Friday.

The case at St. Anne is Waterloo Region's second confirmed case in the school system. Earlier this month, a staff member at Edna Staebler Public School in Waterloo tested positive for COVID-19.

Ristovski said she doesn't think the schools should take any more risks. She said they should shut down now that they've had a case.

"They shouldn't keep going if there's already a COVID case, they should have shut the school down to try to stop it," she said.

She and her family had COVID-19 tests scheduled for Thursday, but Ristovski said she will keep her family in self-isolation for two weeks, even if it returns a negative result.

"If there's one case of COVID and you send the kids back the next day, symptoms take five to 14 days to come out, and if other kids were in contact, my daughter obviously was in contact with them," she said.

"I guess my parents will be doing our grocery shopping."

Ontario has seen an upward trend in daily new COVID-19 cases recently, setting 14-week highs two days in a row earlier this week.

The numbers have gotten so high in some hot-spots—namely Toronto, Peel Region and Ottawa—that on Thursday, Premier Doug Ford rolled back gathering limits in those areas.

The maximum number of people who are now allowed to gather indoors is 10. That number increases to 25 for outdoor gatherings.

Ontario has reported 45,676 cases of COVID-19 since the pandemic began. That number includes 3,294 cases in people aged 19 and under.

With reporting from Heather Senoran