The union representing high school teachers in Ontario says it is planning a one-day strike Wednesday at 16 boards across the province.
It is the latest in a series of rotating strikes the Ontario Secondary School Teachers' Federation has engaged in amid contentious contract talks.
OSSTF members will strike at boards including the Ottawa-Carleton District School Board, Hamilton-Wentworth District School Board and Upper Grand District School Board.
President Harvey Bischof says he'll call off the job action if the government takes class size increases off the table.
Teachers were angered when the province announced in March that average secondary school class sizes would jump from 22 to 28, and though the government has since scaled back those increases to an average of 25 students per class, Bischof says that's not good enough.
Education Minister Stephen Lecce has said such strikes hurt students, and has framed compensation as the sticking point in negotiations.