The Elementary Teachers Federation of Ontario (ETFO) announced Saturday that the Lambton-Kent District School Board will be targeted by the union's rotating strikes next Thursday.
The union said it has sent the five-day required strike notice for Durham, Lambton Kent and Algoma school boards for Thursday January 30.
Public elementary schools across the three boards will be closed that day unless an agreement is reached before then.
ETFO began rotating strikes at select boards across Ontario January 20 in protest of stalled contract talks with the provincial government.
The four major teachers' unions are taking job action in various forms.
ETFO represents 83,000 elementary public school teachers, occasional teachers and education professionals across the province.