The main issues are salary and the cost of health insurance.
The negotiations in District 33 have been underway for 16 months and while they have hit a dead end, the talks continued.
The board had threatened to impose terms of the contract and chief union negotiator Mary Catherine Kosmach said negotiations broke down around 7 p.m. Sunday night.
"They gave us an ultimatum that said we had to agree to everything and then they would talk to us about insurance," she said. "The teachers association has proposed a package that would save the district more money than what the district has on the table."
The board has given the union until midnight Sunday to accept the package offered.
The board has made plans for an interim instructional program and has invited parents to enroll their students in the event of a strike, but it is unclear how long the program would run.
Parents should be prepared for a strike on Monday morning.