The union representing most of the province's public high school teachers announced Friday that it will be striking again on Dec. 11 in certain school boards across the province.

Both Ontario's Education Minister Stephen Lecce and union head Harvey Bischof held news conferences around the noon hour. Each side attacked the other for not being reasonable throughout the bargaining process.

"We are disappointed and mystified at the government's apparent indifference to the legitimate and well-documented concerns of parents, students, and educators alike," Bischof said in a statement.

"Owing to that indifference, our efforts at the bargaining table and our job actions to this point have yielded virtually no progress. We have no choice but to continue our efforts."

Lecce, speaking with reporters at Queen's Park, fired back, saying: "We've made moves. It's now time for them to do the same."

NDP education critic Marit Stiles said Lecce could change the tone of talks by halting plans to increase class size and to mandate e-learning courses.

"The government needs to reverse all these cuts, get back to the table and get a deal," she said.

Green party Leader Mike Schreiner said high school teachers clearly aren't making the move lightly.

"Teachers will not sign off on a plan that pulls thousands of educators out of schools and drags Ontario down to the level of US states that replace teachers with mandatory e-learning," he said in a statement.

All Ontario Secondary School Teachers' Federation (OSSTF) members will be striking in these school boards:

Brant Haldimand Norfolk Catholic District School Board.

Grand Erie District School Board.

Hastings and Prince Edward District School Board.

Near North District School Board.

Rainy River District School Board.

Simcoe County District School Board.

Simcoe Muskoka Catholic District School Board.

Toronto District School Board.

Trillium Lakelands District School Board.

A long list of French schools is also affected.

Earlier this week, the union held a one-day strike that closed almost all public high schools — and even some elementary schools — across the province. The OSSTF represents 60,000 educators.

The teachers, who are already conducting a work-to-rule campaign, say they are pushing back against the Ford government's plans to increase class sizes and introduce mandatory e-learning courses — measures Progressive Conservatives say are needed to trim a $7.4-billion budget deficit.

But the Progressive Conservative government says the key issue at the bargaining table is compensation.

The province has offered a one per cent annual wage increase, but the union is seeking around two per cent.

Lecce says his aim is to 'keep students in class.' (Chris Young/Canadian Press)

Bischof said that the union "absolutely" understands that its job actions are creating a temporary disruption for students and families.

But he said the Ford government's changes to the education system would be worse.

"The Doug Ford agenda, if it is allowed to be implemented, will create long-term disruption for students across the entire education system, and leave publicly-funded education in Ontario deeply and permanently damaged," he said in a statement.

Lecce, however, said the union has dug in its heels and is being "unreasonable."

"Fundamentally, strikes hurt kids. Our aim is to keep students in class," he said.

The minister urged the union to sit down with the government and a third-party mediator in a bid to reach an agreement so students remain in school.