As Ontario students head back to class following March break, some teachers are speaking out about an increase to high school class sizes, saying it will hurt education in the province.

The Doug Ford government revealed significant changes to Ontario's education system Friday, including increased intermediate and high school class size averages.

The average class size requirement for Grades 9 to 12 will be adjusted to 28, up from the current average of 22.

"It's bad news for kids and bad news for schools," said Susan Rab, who teaches law and civics at Sir Wilfrid Laurier Secondary School in Orléans.

"More kids in a class leads to the potential of more issues in terms of classroom management and less time for an individual student to be seen by their teacher," Rab said.

Specialized courses will suffer

Rab said increasing the average class size could also hamper efforts to create smaller classes in more specialized programs, like auto mechanics or Spanish.

She said those courses don't typically attract a large number of students, but high schools are still able to offer them by increasing the number of students in more popular programs.

"If the averages have to be 28, then running a class of 17 becomes incredibly less likely," Rab said.

Luke Simoneau teaches music at Cairine Wilson Secondary School and said he worries about the impact the increased average will have when it's combined with changes the government recently announced to autism funding.

"All of a sudden, it's not six or seven additional kids in the classroom — it's six or seven additional kids who might have fairly high needs," said Simoneau.

Lyra Evans doesn't think the increase to class averages is reasonable based on the work teachers already do. (Adrian Wyld/Canadian Press)

Lyra Evans, the Ottawa Carleton District School Board trustee for Rideau-Vanier/Capital, said teachers already have enough work on their plate.

"I don't see this increase in classroom sizes as reasonable. It's a huge amount. It's not one or two [more students]," said Evans.

Anyone who was asked to do 25 or 30 per cent more work for the same pay would be "justifiably outraged," Evans said.

Change phased in over 4 years

Education Minister Lisa Thompson told CBC News the increase will better align Ontario with other jurisdictions across Canada.

"We saw there was an opportunity to increase class sizes, all the while preparing our high school students for post-secondary education in terms of larger class sizes, and also the real world in employment," Thompson said, adding the change will be phased in over four years.

Lisa Thompson scrums with reporters in 2018. Thompson is promising no job cuts will result from increasing the average class size, but wouldn't say one way or the other whether they would rely on attrition to cut costs. (Chris Young/Canadian Press)

The government is also promising jobs won't be cut because of the change, but Thompson wouldn't say whether they'd rely on attrition to cut costs.

"It's too early to tell right now, and we'll be working with our school boards to identify other ways that we could possibly reduce spending," Thompson said.

"And also, we'll be working with them to assess what the retirement pattern is."