TORONTO -- Ontario's premier is raising the possibility of back-to-work legislation for striking teachers, as thousands of students have been out of school for nearly five weeks.

The Liberal government is waiting on a ruling from the Ontario Labour Relations Board on the legality of the strikes, and is also awaiting advice from the Education Relations Commission on whether the students' school years are in jeopardy.

Once those rulings and recommendations are in, the government would act, said Premier Kathleen Wynne.

"I will take whatever action that I need to take to get the students back to school as quickly as possible," she said Thursday.

When asked if that included back-to-work legislation, she responded, "if that's what we have to do."

More than 70,000 students have been kept from class for weeks as high school teachers strike in the Sudbury-area Rainbow District, Peel Region and Durham Region. The strike in the Durham District School Board has lasted nearly five weeks.

The school boards argued at the labour board that the teachers have been largely protesting about class sizes, which is a central issue, and in the boards' opinion, legislation the Liberal government passed last year prevents local strikes on central issues.

The School Boards' Collective Bargaining Act -- passed last year -- was intended to bring clarity to labour negotiations, separating the bargaining process into local and central talks.

But the act came under fire as not clear enough this week at the labour board. The law doesn't explicitly ban teachers from staging local strikes on provincial issues, but the boards argued that's what it was meant to do.

The Ontario Secondary School Teachers' Federation lawyer said the school boards are "in essence asking the board to read into the act a requirement that is not there, a requirement to scrutinize the conscience, hearts and minds of striking workers -- a task which is as invasive as it is impossible."

Wynne said the legislation was crafted in conjunction with the school boards and unions, but would not comment on whether its intent was to ban local strikes on central issues.

"We have put in place a process that recognizes that there is a central-provincial process that needs to take place and there are local processes," she said.

Progressive Conservative education critic Garfield Dunlop said the act should be fixed before the end of this session "so students won't be used as pawns in this way again."

"There is still potential for the Catholic and French boards to strike in the next few months," he said in a statement. "We don't need this chaos to spread even further."