Public high schools across Ontario are shut down today as teachers stage a one-day strike amid tense contract talks with Doug Ford's government.

The moves affect public school boards, tens of thousands of students and parents left scrambling to find alternate arrangements for their children. Some after-school and night programs were also affected by the walkout.

The Ontario Secondary School Teachers' Federation (OSSTF) launched the strike at midnight Tuesday night following another failed day of negotiations with the government. Some 40,000 high school teachers and 20,000 support staff represented by the union walked off the job Wednesday.

The union has had difficult negotiations with previous provincial governments, but this is the first time since 1997 its members have gone on strike. Speaking with reporters on a Greater Toronto Area picket line, OSSTF president Harvey Bischof said teachers will be back on the job on Thursday, but he didn't rule out future strikes.

Bischof said the union is committed to giving parents five days notice before launching any future strike.

Some 40,000 high-school teachers and 20,000 support workers walked off the job for a one-day strike. (Michael Cole/CBC)

The closures affect the majority of Ontario's high schools, although most Catholic secondary schools remain open.

However, in some cases Catholic, French, or elementary schools have been forced to close as a result of the strike.

In Ottawa, for example, there are enough OSSTF workers in some elementary schools that public boards were forced to shut.

Ford's government is also locked in contract talks with public elementary teachers, who are currently staging a work-to-rule campaign, and English Catholic teachers, who will be in a legal strike position before Christmas.

Teachers are expected to set up picket lines at local schools Wednesday.

"As a parent, I'm out here for my kids to make sure that they get the education that was afforded to kids over the last 20 years," said Dan Retson, a teacher of 13 years.

"That's more important than one day and the inconvenience that it causes me and all the other parents."

Hundreds picketed outside Toronto District School Board headquarters after the union and the province failed to come to an agreement. (Michael Cole/CBC)

In the crowd of picketers was a sizable group of support workers who are members of the union and have also seen their fair share of cuts. They say their services are essential, especially for vulnerable students.

"You're putting young people at risk when we do not invest in the supports that they need," said Kimberly Perry, president of the Professional Student Services Personnel in Toronto.

Students march in solidarity

"These are young people who may have different mental health challenges, physical difficulties. They may have learning disabilities," she said. "The professional supports are the ones that make sure that they have equitable access to the system."

While some students are happy to be sleeping in, others backed the teachers by marching at Riverdale Collegiate Institute in the city's east end Leslieville neighbourhood.

We should be in class today, but we should not be forced to sit in sub-par classrooms. - Ivy Deng, Earl Haig high school student

Ivy Deng, a student trustee with the Toronto District School Board, the city's largest, said students are supporting teachers because they are defending their education.

"We're finally being heard. We're finally being fought for," Deng said.

Her school, Earl Haig, has struggled with large class sizes this year particularly for courses including math and English.

Deng said she thinks the teachers, not the government, are more committed to dealing with that problem.

"We should be in class today, but we should not be forced to sit in sub-par classrooms."

Ontario Education Minister Stephen Lecce hasn't been able to reach a deal with the province's teachers' unions. (Christopher Katsarov/Canadian Press)

Eesha Chauhan, a Grade 11 student at Riverdale Collegiate, also highlighted concerns with class size.

"I had to drop my math course," she said, adding that with 42 students in one room, she found it too loud to learn.

Chauhan said she now plans to take math as a night course.

Union, government appear to be struggling with talks

Also Wednesday, Education Minister Stephen Lecce blasted the union, calling the one-day strike "unacceptable" for Ontario families.

"Our students deserve to be in class today," he told CBC Radio in the morning.

Lecce defended his government's role in bargaining, saying it had made a number of moves at the table. However, he said the union has rejected the government's ask that it come up with its own proposals to help cut costs in the education system.

"They've said no, no and no."

The Ontario-wide public high school teachers' strike is unfair to families, says Education Minister Stephen Lecce; Toronto high school students Ivy Deng and Eesha Chauhan say "his actions don't match his words". 16:10

Leslie Wolfe, president of the OSSTF in Toronto, along with other leaders in the union say they haven't seen an offer from the minister at all.

"There was no new proposal. It was independently confirmed by the mediator that there was no new proposal and none of us know what Mr. Lecce was talking about when he said that," Wolfe said.

According to the union, the main issues are government plans to increase class sizes and introduce mandatory e-learning courses. According to the government, the prime issue is compensation.

"It seems to me that the salary is most important to Mr. Lecce and publicly funded education is least important to Mr. Lecce," said Wolfe.

Premier Doug Ford weighed in on the strike, saying Wednesday afternoon he has all the confidence in the world in the minister to sign a deal and stay on the stance that the union has not been reasonable.

"It's kind of one-sided so far," he said.

"We're negotiating in good faith. We have given a couple of concessions, as a matter of fact, quite a few concessions. I guess the union's not giving us any concessions."

Lecce wouldn't confirm if he had offered to reconsider class size increases if teachers would agree to one per cent wage increases, but indicated that's the pay increase the government is offering.

The OSSTF has been without a contract since the end of August and started a work-to-rule campaign last week.

Schools shut down by the one-day walkout include those at these boards: