TORONTO -- It will be several days before 70,000 Ontario high school students can return to class after the New Democrats delayed Monday the passage of new legislation that would force striking teachers back to work.

The Liberal government tabled back-to-work legislation after an arm of the Ontario Labour Relations Board advised the province that the school year was in jeopardy for students in three boards where teachers have been on strike for up to five weeks.

Failure to win unanimous consent to get the bill passed on Monday means it will be pushed back several days, and Friday is the earliest students in the Sudbury-area Rainbow District, Peel Region and Durham Region could return to class.

Students could have been back in class Tuesday with all-party support, and Premier Kathleen Wynne said she was "disappointed" the NDP would stall the legislation's passage.

"I don't actually understand where the philosophical problem is here, because they know that these kids are at risk and they also know that there is ample opportunity for us to continue to try and get a deal," she said.

Education Minister Liz Sandals said the government respects the collective bargaining process, but it's important to get kids back to class to complete their school year, which she does not expect to be extended beyond June 30.

The Progressive Conservatives "reluctantly" supported the legislation, while NDP Leader Andrea Horwath called it "undemocratic" and said that the chaos in the education system is of the Liberals' own making.

This is the first round of negotiations under a new bargaining system the Liberal government introduced last year, separating the process into local and central talks.

As the high school teachers in the three strikes are being legislated back to work, the Ontario Secondary School Teachers' Federation is raising the possibility of a provincewide strike, while their elementary counterparts enter the third week of an administrative strike.

Central talks between high school teachers and the province broke down over the weekend and the OSSTF has applied for conciliation, which could set the stage for a provincial strike.

"We're looking at where we can go in the fall," said OSSTF president Paul Elliott.

"It's become quite clear the boards won't negotiate with us locally. We're at an impasse at the central table. We're reassessing where we're going to go at that central table."

If there is a provincewide strike before September, it would not be allowed to affect the Durham, Rainbow and Peel boards, Sandals said. Bargaining in those boards should be sent to arbitration but with the use of a mediator, the Education Relations Commission recommended.

The Ontario Labour Relations Board had also been set to rule on whether the three local strikes were illegal.

That ruling will still be of interest as the government conducts a review of the new legislation following this round of bargaining, Sandals said.