The Zion-Benton Federation of Teachers has filed an "intent to strike notice" with the Illinois Educational Labor Relations Board.
It claims the board of education from Zion-Benton Township High School District 126 refused to return to negotiations after declaring an impasse in October.
The union's action will allow it to strike after a 10-day waiting period.
The union represents nearly 300 employees.
ABC7 was unable to reach the school district for a comment.