The Elementary Teachers' Federation of Ontario say the legislation is unnecessary and tramples on their constitutional rights.
The teachers' federation has issued a call for teachers and school workers to join the rally.
Ontario's governing Liberals introduced the controversial legislation on Monday that will force new contracts on thousands of Ontario teachers.
The bill would rein in wages and cut benefits, as well as give the government the power to ban lockouts and strikes, which some unions are condemning as an unprecedented attack on their constitutional rights.
If the legislation doesn't pass, old contracts with Ontario teachers will automatically roll over, giving them pay raises and benefits the Liberals say the province can't afford. The governing Liberals hope to have the bill passed by next week.
The teachers say there will be no labour disruptions this fall, but aren't ruling out job action later in the year.
Meanwhile a major union representing secondary school teachers agreed to postpone strike votes that were planned for Monday. In a news release, Ontario Secondary School Teachers' Federation (OSSTF) union president Ken Coran said the strike votes are being suspended, a move Education Minister Laurel Broten called "encouraging."
The minority Liberals need support from one of the opposition parties to pass the legislation.
Opposition Leader Tim Hudak insists his party will support the bill, while NDP Leader Andrea Horwath has said she will not.
Hudak said he would prefer a bill that imposes province-wide public sector wage freezes, something Premier Dalton McGuinty says is unconstitutional.
Key byelections looming
NDP house leader Gilles Bisson said the Liberals are trying to create a crisis to win two potentially game-changing byelections on Sept. 6.
The Liberals have a shot at a majority government and are willing to do whatever it takes to win in Vaughan and Kitchener-Waterloo, no matter what the cost, he said.
The Elementary Teachers' Federation of Ontario, which represents 76,000 teachers, said it's calling on teachers to volunteer in the riding of Kitchener-Waterloo, which was previously held by the Tories.
McGuinty made an appearance in Waterloo on Monday and dismissed suggestions that his government had manufactured a crisis.
"This is a lot bigger than any one byelection," he said. "It affects two million students and 125,000 teachers."
It's important that voters consider the Liberals' approach to the issue in contrast to the two other parties, who are swinging too far to the left or right, McGuinty said.
"But the fact of the matter is, this is of real interest and concern to parents everywhere," he added.
At present, the Liberals hold 52 of the 107 seats in the Ontario legislature. If they manage to win both seats up for grabs in the byelections, they would regain the majority control they held at Queen's Park prior to last October's election.
The seat in Kitchener-Waterloo was previously held by long-time Progressive Conservative MPP Elizabeth Witmer until she resigned to take a job with the Workplace Safety and Insurance Board.
Greg Sorbara stepped down from his seat in Vaughan earlier this month, though he remains involved with helping the Liberals prepare for the next election.