TORONTO -- Elementary school teachers in Ontario will start an administrative strike next week as the province's education minister says the move is motivated by the union's "general desire to have a strike" rather than any one issue.

The planned job action comes as more than 70,000 high school students in the province sit home because teachers at three school boards -- Durham, east of Toronto, Rainbow, encompassing Sudbury, Ont., and surrounding regions, and Peel, west of Toronto -- are on strike.

The Elementary Teachers' Federation of Ontario told members they will be on a work-to-rule campaign starting Monday that will include their refusal to administer standardized tests, to prepare report cards and to participate in professional development sessions.

Education Minister Liz Sandals said Monday she has heard from government negotiators at the contract talks that the labour unrest isn't about one issue in particular.

"It just seems to be a general desire to have a strike," she said. "The conditions to not have a strike were pretty unrealistic. I'm not going to get into the individual issues."

The union said it's taking action in response to government demands that would "strip collective agreements, reduce teachers' ability to use their professional judgment when providing instruction and compromise students' learning conditions."

The government wants to remove class-size language from collective agreements, which would allow school boards to increase the number of students in elementary classrooms, and to direct teachers on how to spend their preparation time, ETFO said in a statement.

When asked if she was considering back-to-work legislation, Premier Kathleen Wynne said the Education Relations Commission determines when a strike or lockout places a school year in jeopardy for students, and that has not happened yet.

In order for the commission to make that determination, it would have to get a request from a school board to consider it. The Durham District School Board, where students have been kept from class since April 20, did not immediately comment.

Sandals said based on the commission's previous decisions, weighing how long a strike has lasted and how close it is to the end of the school year, it would likely not rule yet that the Durham students' year is in jeopardy.

The school board was able to get Grade 12 students' interim marks into universities and colleges before the strike, Sandals said.

Central talks between the Ontario Secondary School Teachers' Federation and the province and school boards have also broken down.

This is the first round of negotiations since the province brought in a new bargaining system with both local and provincial talks. Wynne said she knew this knew system would be tough, and it is proving difficult for local negotiators to reach settlements before there is a central deal.

"The only thing that I can do is to get that deal," she said. "It is my responsibility to light whatever fires I need to light under our folks to get that deal and to get it in a way that fits within our parameters."