Toronto Public Health’s recommendations that the Toronto District School Board reduce class sizes below provincial guidelines is the latest knock against Premier Doug Ford’s schools reopening plan.

“The number of students in the classroom should be smaller than usual class sizes,” in order to ensure proper physical distancing and reduce the risk of virus spread, the letter dated Thursday sent from associate medical officer of health Vinita Dubey said, noting Toronto Public Health has “concerns” about the board’s plan that is in keeping with the province’s decision on class sizes.

The letter, received by Carlene Jackson, the board’s interim director of education, was shared with trustees and first reported by the Globe and Mail. A copy was viewed by the Star.

In a message to trustees, Jackson said she asked Toronto Public Health to put its thoughts on the board’s back-to-school plan in writing.

Dubey specifically mentions the Ford plan to allow full-sized elementary classes where children in Grade 3 and below would not be required to wear masks.

“In elementary classes (JK to grade 3) where masks are not required, smaller classes sizes will particularly be important to ensure students can be spaced out and reduce transmission,” the letter says.

It goes on to note the scientific evidence that keeping a distance of two metres “works well to prevent the spread of respiratory droplets from one person to another.”

Ford’s plan to reopen schools has been under fire since it was unveiled last week, especially over the decision to keep elementary class sizes as is.

Boards, including the TDSB, have been preparing plans in line with the provincial guidelines.

In an emailed statement Thursday night, Alexandra Adamo, spokesperson for Education Minister Stephen Lecce, said: “Our plan to safely reopen schools has been informed by the best medical and scientific minds in the country — Ontario’s Chief Medical Officer of Health, Dr. David Williams, the COVID-19 Command Table, and the Hospital for Sick Children.”

She called the provincial plan a “living document” that can be adapted to “apply the best advice as it emerges.”

“We will never hesitate from taking further action to protect the health and safety of Ontario’s students and education staff.”

Earlier, SickKids and other children’s hospitals said reducing class sizes should be a “priority strategy” to help limit the spread of COVID-19.

Toronto Public Health’s position on the province’s plan has not previously been made public.

An online petition calling for a reduction in Ontario class sizes had reached over 173,000 signatures as of Thursday night.

Jennifer Pagliaro is a Toronto-based reporter covering city hall and municipal politics for the Star. Follow her on Twitter: @jpags