Ontario's public high school teachers are expected to be back in class today following a one-day strike.
But the union representing them says Wednesday's walkout could be the first of many if the government doesn't change course in contract talks.
The Ontario Secondary School Teachers' Federation, which represents about 60,000 public high school teachers and support workers, says it is pushing back against government plans to increase class sizes and introduce mandatory e-learning courses.
The teachers are already conducting a work-to-rule campaign and say they would give five days' notice before any further labour action.
Education Minister Stephen Lecce called the one-day strike unacceptable and urged the union to take part in private mediation.
Lecce has also said the union must bring new proposals to the bargaining table, not just reject the government's offer.