BARRIE, ONT. -- "The more distancing we can support, the better," Ontario Education Minister Stephen Lecce said on Thursday during a media briefing.

After criticism and calls from parents, teachers' unions and school boards to shrink class sizes, the minister pledged access to nearly $500 million in reserve funds to help ensure physical distancing in select schools.

"This investment does that," Minister Lecce added, saying the funding allows for an "element of flexibility and latitude."

The Ford government pledged another $50 million in funding to improve air quality in schools with ageing HVAC systems.

Ontario's Chief Medical Officer of Health Dr. David Williams said he stands behind the government's back-to-school plan but, at the same time, acknowledges that there is "no such thing as a totally risk-free setting."

"We feel that we're well prepared to move in," Williams said. "If something does happen, if there is a case, we're going to move to quickly contain it, inform you, educate you and advise you of what you need to do."

With an average of about 100 confirmed cases a day in the province, Dr. Williams said the virus appears to be under control.

The education minister said school boards could use the "one-time investment' to deal with physical distancing as they see fit. "It allows them to support the leasing of additional space should that be requested for distancing."

Before the minister's announcement, Ontario's four major teachers' unions released a joint statement alleging the province's back to school plan violates its own occupational health and safety legislation.

The unions - which represent some 190,000 teachers and education workers - have argued for smaller class sizes, something Minister Lecce said today he would not mandate at this time.

With files from CTV Toronto and The Canadian Press