The governing Liberals have reached a new labour deal with the Ontario English Catholic Teachers Association.
Education Minister Laurel Broten says the union, which represents 45,000 teachers, has agreed to a two-year deal with no salary increase.
It's the first teachers group to break ranks with the other unions, who have refused to negotiate after they were told their wages would be frozen.
The Liberals are trying to get workers in the broader public sector to accept a wage freeze as they battle a $15-billion deficit.
They've said they'll legislate the freeze if all other options fail.
McGuinty has said his government will work as hard as it can to secure agreements before school starts in September.