It's a sign that more deals can be reached to save the school year from further strike action, he said.
"I'm hopeful that these agreements will act as a bit of a template for other boards around the province and this will get the ball rolling," McGuinty said.
But there are many more to go.
About 35,000 high school teachers and education workers are continuing their strike action in 28 school boards across Ontario. About 5,000 elementary teachers have joined in, with more to come.
Within the next two to three weeks, all elementary teachers are expected to be in a legal strike position, opening the door to provincewide strike action.
McGuinty acknowledged it's a steep climb, but said the two deals act as a "beacon" to other boards and union locals.
"I don't think we should enlarge these two deals beyond what they represent, but neither do I think we should diminish their significance," he said.
Five school boards have reached tentative agreements with high school teachers, but the government has only approved two so far.
York Region and Upper Grand District school boards received the Liberals' blessing, pending some fine-tuning at the local level and ratification by the boards and their union members.
Hamilton-Wentworth, Thames Valley and Niagara District school boards are still waiting for the green light.
There's pressure to reach a deal, since the Liberals now have the power to impose their own agreement if they don't like what the unions and school boards negotiate together.
Any tentative deal must be similar to the one the Liberals struck with English Catholic teachers, which froze the wages of most teachers and cut benefits, such as the banking of sick days that can be cashed out at retirement.
Four unions are taking the government to court over a new anti-strike law that's granted the Liberals these unusual powers, arguing it's unconstitutional and violates collective bargaining rights.
Job action among teachers has been escalating from the initial withdrawal of volunteer activities — such as coaching sports teams — to skipping certain tasks, such as administering standardized tests and keeping report card comments to a minimum.
Elementary teachers in York Region, which includes 120,000 students in nine municipalities north of Toronto, were the first to join their high school counterparts Monday in taking strike action. It included arriving no earlier than 30 minutes before class started and leaving no later than 30 minutes after students were dismissed for the day.
The minority Liberals have so far refused to use their power to stop the job action.
They brought back the legislature early to introduce the legislation, and now they're not even using it, said Progressive Conservative Steve Clark.
"It's a bit of a surprise that the government brought us back, there was this great sense of urgency, and it continues to be a mess," said Clark, whose party supported the bill.
McGuinty is desperate to clean up the mess he's created with Bill 115, said New Democrat France Gelinas, whose party opposed it.
Only two deals have been approved and there are 29 other school boards who still need to negotiate agreements with teachers.
"This is supposed to be a groundbreaking announcement? It is not," Gelinas said. "It just shows how pathetic the whole thing has become."
The Liberals' relationship with public sector unions has soured considerably since the passage of Bill 115, which the Tories supported.
When he arrived to give a speech at the Ontario Nurses' Association convention in Toronto Tuesday, McGuinty received applause, but was also booed by a small group of delegates.
It was a marked departure from the standing ovations the premier has received in a past.
"We heard the quiet booing, people crossing their arms, refusing to clap," said Gelinas, who attended the speech.
"They want to show that they're not happy with their premier."