Strikes will take place at eight school boards, including the Toronto District School Board and seven others in southern and central Ontario.
The Elementary Teachers' Federation of Ontario has said it will give 72-hours notice of any walkouts as teachers continue to protest a law allowing the government to stop strikes, freeze wages and cut benefits.
On Wednesday, it will be the Bluewater board, which includes Owen Sound, Bruce and Grey counties, the Algoma board in the Sault Ste. Marie area of northern Ontario, and the Halton board, which includes the Burlington and Oakville areas west of Toronto.
Thursday's walkouts involve the Thames Valley board, which covers Elgin, Middlesex and Oxford counties and includes London, Woodstock and St. Thomas; and the Limestone board which covers Lennox and Addington county and Frontenac county, which includes Kingston, in eastern Ontario.
Also targeted on Thursday are the Superior-Greenstone board in northwestern Ontario and the Upper Canada board in the Brockville area of eastern Ontario.
Premier Dalton McGuinty has said the government would allow the one-day strikes as long as they don't extend beyond that.
(The Canadian Press, CJOJ)