TORONTO -- Ontario's public school elementary teachers will stop performing some administrative duties Monday in what they're calling Phase One of a province-wide strike.

Teachers will still be in the classrooms and extracurricular activities and field trips will continue for now. They will not be administering any standardized tests, adding any comments to report cards beyond the marks, nor will they participate in any meetings or professional development related to Ministry of Education initiatives.

The Elementary Teachers' Federation of Ontario president left open the door to escalating the job action.

"This strike action is incremental in nature," Sam Hammond said Friday. "It will continue in its current form until (the government and school boards') demands are withdrawn from the bargaining table or ETFO deems that further actions are required."

He would not say what a second phase could entail.

Hammond said the Liberal government and the Ontario Public School Boards' Association has refused to remove demands that would "strip" teachers' collective agreements, increase bureaucracy and "handcuff" teachers.

The union told its members about the work-to-rule in a memo earlier this week, but refused to confirm it publicly until Friday at 2 p.m.

Hammond said his members will not allow school boards to increase class sizes, but the Ontario Public School Boards Association said it's incorrect to suggest it is advocating for that.

The teachers' union is demanding that all of the OPSBA proposals be withdrawn from the table, which is unreasonable, said its president Michael Barrett.

"The concept of negotiation is to be able to put positions on the table then bargain...in order to be able to come to a compromise," he said. "Withdrawing all our items on the table to only be concerned with items they have on is not bargaining."

Education Minister Liz Sandals said in a statement that she is disappointed ETFO is withdrawing some services, she is "encouraged" that students will remain in the classrooms.

The elementary strike comes as more than 70,000 high school students in the province sit home because teachers in the Toronto-area boards of Peel and Durham, as well as Sudbury, have walked off the job.