The latest twist in talks between the educational sector and province could close schools, even if teachers stay on the job.
The union representing Ontario school support workers says job action will begin on the first week of school.
Its membership voted overwhelmingly on the weekend to work to rule in Septmeber.
The Canadian Union of Public Employees says the plan will gradually increase to rotating strikes, and eventually ramp up to a sweeping, province-wide strike.
Workers affected include educational assistants, office administrators, custodians, IT specialists, and many others.
