The teachers say they have exhausted their options at the bargaining table following no board reports through conciliators.
The Avon Maitland District School Board has schools in communities such as Stratford, Wingham and Goderich, while the Ontario North East District School Board covers communities such as Timmins, Kirkland Lake and Iroquois Falls.
The union says the strike is to protest the legislation that gives Education Minister Laurel Broten the ability to stop strikes by teachers and lockouts, and impose a collective agreement.
Meanwhile, the Elementary Teachers' Federation of Ontario says a solid majority of elementary teachers across the province have voted in favour of a one-day political protest if Broten uses the provisions of Bill 115 to shut down strikes or impose a collective agreement.
Broten has scheduled a news conference for Thursday morning to address the one-day strikes announced by the teachers in Avon Maitland and Ontario North East.
"I understand parents are concerned about the impact of this on their families," Broten said Wednesday in a release.
"I am taking the time to consider all the options available to our government," she said.
The ETFO said 92 per cent of more than 46,000 members who cast a ballot during an online vote earlier this week voted in favour of a one-day political protest if Broten uses Bill 115.
"This vote affirms once again that it is our members who determine their actions through democratic processes, contrary to Minister Broten's derogatory comments about union leaders this week," ETFO president Sam Hammond said in a release.
"It is unfortunate that her government crafted a law that allows no judicial appeal in the provincial courts — a tactic rarely, if ever, used in democracies," Hammond said.
"Our members have been left with little recourse but to choose a political protest."
North East Occasional Teacher Local president David Livingston said the decision to strike on Monday was not made lightly.
"For the first time in our 14-year history, Ontario North East ETFO members will be forced to take full-scale job action," Livingston said.