"The temperature — or the dial — has been turned up a notch," Ken Coran, the president of the Ontario Secondary School Teachers Federation said at a press conference in Toronto.
Coran said that while extracurricular activities will stop after Dec. 10, there will not be any strike action at this point.
"Our members will continue to deliver curriculum. They will be in the classroom every day," he said.
"We are very hopeful that the public will see that we are trying to do what is best for the students."
The move comes as some elementary school teachers in Niagara and Guelph have stepped up their job action, refusing field trips and other out of classroom activities.
The OSSTF cut off talks last week after teachers rejected local agreements with two school boards. Ratification votes for any other tentative agreements have been suspended until further notice.
It was revealed Sunday the federation scrapped its tentative agreement with the Ottawa-Carleton District School Board and teachers would resume administrative action.
The union is responding to a controversial wage freeze bill that it said has hamstrung its efforts to reach fair agreements with local school boards by putting major restrictions in the way.
There are 29 "mandatory" job sanctions for public high school teachers, sent out over the weekend, which included instructions not to issue progress reports or participate in field trips, staff meetings or crafting any learning plans.
Unassigned supervision of student behaviour in hallways is expected to continue, though.
Unions 'sought conflict,' education minister says
OSSTF spokeswoman Lori Foote has said the tentative agreement was scrapped due to "ministerial intervention."
Education Minister Laurel Broten argued Monday there had been no interference in local bargaining. She told reporters the unions for elementary and high school teachers should call off the strikes.
Broten accused the union of seeking conflict instead of resolving outstanding issues before Dec. 31, the deadline for boards and unions to agree on new deals across Ontario.
"The actions by the teachers' union leadership show clearly that this was never about bargaining locally and finding solutions," said Broten.
"This has been, and will continue to be, about the refusal of union leadership — not our teachers — to accept a real pay freeze."
Broten also told the unions to "take your fight to courts" instead of affecting students.
The unions have gone to court to challenge Bill 115, which freezes the wages for most while allowing younger teachers to still move up the salary grid. Unions argue it infringes on their right to collective bargaining and has hamstrung efforts to reach fair agreements with school boards.
The bill is modelled on an agreement the province reached with unions representing Catholic and Francophone teachers.
Public elementary schools to increase job action
In Ontario's English public elementary schools, teachers are expected to hold strikes over the next few weeks. The Elementary Teachers' Federation of Ontario said it would give parents 72-hour notice before teachers walk off the job.
Starting Monday, elementary school teachers have stopped performing some out-of-class duties within their contractual obligations including administrative and non-instructional duties such as extracurricular activities, field trips, meetings, professional development, provincial assessments and any activities outside of the regular school day.
Ottawa's public school board has announced all its elementary schools will close if elementary and occasional teachers unions hold a one-day walkout across Ontario. Those two unions are now in a legal strike position.
Toronto elementary teachers, who will be in a legal strike position on Dec. 10, will be notified there will be a one-day strike before Dec. 21, according to the representative from York Region's elementary teachers' union.
That strike will affect students in Canada's largest school board in Canada, with nearly 600 schools serving about 250,000 students.
The education minister reminded the province’s teachers last week her government has the "legislative tools" to impose a labour agreement if elementary teachers proceed with plans to strike.
The governing Liberals can stop the impending strikes by imposing a new collective agreement on teachers. They can also prohibit certain strike actions.
The ETFO said it would provide an update on job action Tuesday.