The teachers picked the Avon Maitland school district near Goderich and the Ontario North East district near Timmins to begin with. They say the strikes will move to Ottawa Wednesday and the Greater Toronto Area Thursday, the Canadian Broadcasting Corp. reported.
The Elementary Teachers' Federation of Ontario has said it will give 72 hours' notice before any job action.
The Ontario Secondary School Teachers' Federation says its members were to quit doing any non-classroom work such as spots and holiday concerts starting Monday.
Union officials say the strikes are to show teachers' opposition to legislation that gives the government power to stop strikes and impose collective agreements.
Ontario Premier Dalton McGuinty has said no effort would be made to stop the walkouts because they are for one day each with advance notice.