The agreement between the Ontario Secondary School Teachers' Federation (OSSTF) and the York Region District School Board was reached just before 5 a.m. Saturday.
Board spokesman Licinio Miguelo says details in the contract will likely be sent to Ontario Education Minister Laurel Broten on Monday.
Miguelo says the board and the union have been in negotiations since early June.
Media reports say a deal has also been reached between the union and the Upper Grand District School Board in Guelph.
"I am very pleased that tentative agreements have been reached between OSSTF locals and two local school boards," Broten said in a statement.
"I look forward to receiving the agreements in the days ahead to confirm that they meet the substantively identical test laid out in the Putting Students First Act. Reaching negotiated agreements that meet our shared fiscal challenges while protecting small class sizes, full-day kindergarten and teacher jobs has always been our preference."
Earlier this week, the OSSTF advised its 60,000 members to begin a series of "strike actions" such as skipping staff meetings and not communicating with parents outside of school hours.
The province is facing a $14.8-billion deficit and has passed legislation freezing teachers' wages and taking away their right to strike.
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