As students, parents and teachers prepare for two more weeks of online learning during the COVID-19 pandemic, the head of CHEO says adults have let children down.

On Thursday, the Ontario government announced elementary schools in Ottawa an across southern Ontario (south of Sudbury) will remain closed until Jan. 25. Elementary students were originally scheduled to return to class on Monday, following one week of online learning after the Christmas break.

"There's no question that the impact of closing schools is devastating for children, it's hard on families; so this is a heartbreaking day," said CHEO President Alex Munter during an interview on CTV News at Six.

"Also, we know how to prevent COVID and we haven't been able to do that; and that's on all of us as adults. I think the story is here is that as adults, we've let kids down."

CTV News at Six anchor Patricia Boal asked Munter why it might be harder for children to learn online, rather than back in the class.

"For some kids, it's just not possible.  I think of parents of kids with special needs, parents that are not able to be at home; there are many reasons why this is extremely difficult from a mental health and a developmental prospective for kids."

On Twitter, Munter said governments, communities and individuals have "failed our children" by not taking steps to prevent COVID-19.

"The fact is we've always known that what makes schools unsafe is less about what's happening inside schools, then what the rate of community transmission is," said Munter on CTV News at Six.

"Here in Ottawa, all the indicators are going in the wrong direction. We have a record high number of cases; our COVID in the wastewater is going up; our hospitalizations are increasing – all the trends are in the wrong direction."

Premier Doug Ford said he received new data Wednesday night that indicates COVID-19 positivity rates amongst children have been increasing.

"I understand why the government has made this decision, but I think it's going to be really, really important for us to bring those rates of transmission back down again so that the schools can reopen," said Munter.

"The schools should be the last to close and the first to open."

Infectious Disease Specialist, Dr. Isaac Bogoch told CTV Morning Live on Friday that he believes the Ontario government had to extend the school closure.

"When you look at the percent positivity in the kids, especially over the holiday season, it was going to be clear that you were going to bring more COVID-19 into schools than had ever been brought in before, also factor that growing community burden," said Dr. Bogoch.

"That just means the probability of transmission in the schools is going to go up. I think they were going to be in for a very tough January in the schools."

Dr. Bogoch says the next question will be, what metric will the Ontario government use to determine when it's safe to reopen schools for in-person learning.

"Unfortunately, we're in for the roughest period of the pandemic here in Canada. We’re now two weeks after the holiday season started, we're seeing record high numbers of cases," said Dr. Bogoch.

"January is going to be very ugly; this isn't going to get better anytime soon. It's going to take weeks and weeks and weeks for this to start to improve and I'll be very curious to know when they feel it's safe to put kids back into school, even with additional measures in place."

Back at CHEO, Munter says the hospital and all child and youth mental health agencies are seeing an increase in children accessing mental health resources during the pandemic, including a spike in eating disorders.

"Many, many more patients than we've seen before, really overflowing our eating disorder unit as well as depression and anxiety. Much more severity mental illness than we would normally be seeing," said Munter.

"For sure, there's a huge impact; school is so important for kid's development, for their mental health, and of course for their education. It's important for families, it's important for the economy."