However the teachers union chief negotiator Mary Catherine Kosmach said no strike date has been set.
The union filed its intent to strike Friday.
Union officials and the school board are stuck in negotiations over several issues including salary, class sizes and health insurance.
The district needs to balance the budget and in order to do that it must cap the amount it pays teachers for health insurance, according to the school board president.
"On December third, the District 33 Board halted negotiations and declared impasse," Kosmach wrote in a press release. "The board's action made a difficult situation even more divisive, and for the first time made a strike a real possibility."
Kosmach said the union still hopes a strike will be avoided with "an agreement through mutual compromise with the school board".
The Associated Press contributed to this report.
