Students in Ontario, Quebec, Manitoba and Nova Scotia allowed back in school amid Omicron

Millions more Canadian students are allowed back to school Monday, as officials across four provinces work to keep classrooms safe from COVID-19 and the threat of Omicron-driven staff shortages.

Students spent the start of the New Year online because of record-high case counts. 

The provinces said the return to remote learning was intended to take pressure off the health-care system and give schools more time to improve safety measures.

Deploying rapid antigen tests and upgrading air quality in schools are among the steps governments say they've taken ahead of the return to class, with some of the work still underway. 

Still, some parents and teachers' unions are voicing concerns that those efforts won't be enough to keep classrooms safe and ensure there's enough staff available to keep schools operating. 

Officials and school boards have told parents there are contingency plans in place, but to expect potential shifts back to online learning if the virus' spread forces enough people into isolation. 

Students in Waterloo Region and much of southern Ontario will have to wait until at least Tuesday to return to school, with a winter storm forcing schools in this part of the province to close for the day, and students will have to learn online for at least one more day.