KITCHENER -- The Ontario Ministry of Education is shipping three-layer masks to Waterloo Region's school boards for what they say will be a back-up supply.

John Shewcuck, the chief managing officer for Waterloo Catholic District School Board, says masks are still the number one school supply as students make their return to classes.

"It's really important they do mask up at all times," he said. "These masks will help them be able to do that.

"Having three layers is obviously more protective than one layer, both on the outgoing spread with anything that might be coming from somebody and also the intake coming from the other side."

In a statement, the ministry says they're sending out 3.5 million three-layer cloth masks to school boards for the second semester to supplement the students' own supply.

“As children return to school, they are even safer with tougher measures to protect students from COVID-19. We've supported access to a higher quality of three-ply mask for our youngest kids, and introduced active screening of secondary students and of staff before they enter our schools," Minister of Education Stephen Lecce said in an emailed statement on Wednesday. "We will continue to act, adding new layers of prevention and investment every step of the way to build up our nation-leading plan so that our classes are safe for all children and all staff in our province.”

It will take some time to package the masks properly once they arrive, according to the Catholic board, but they're still expected to be sent home with students in about a month.

"The recommendation [from the province] continues to be that people have at least the recommended cloth masks," said Dr. Hsiu-Li Wang, Region of Waterloo Medical Officer of Health.

The Public Health Agency of Canada recommends a non-medical mask should be at least three layers. Two of the layers being tightly woven material fabric like cotton or linen, while the third middle layer should be a filter-type fabric.