TORONTO -- Ontario will soon enshrine in law a process for labour negotiations with the province's teachers, but critics say it won't stop instructors from depriving students of cherished extracurricular activities if talks break down again.

The new law, which passed Tuesday, entrenches the current system for collective bargaining talks with some adjustments, something the Liberals were pressed to do after inflicting major damage on its relationship with public school teachers two years ago.

When the last round of negotiations fell apart, the Liberals forced new contracts that froze some teachers' wages and prevented them from striking, igniting a war with a very influential source of political support.

School boards also complained that they were left out and had no say in the tentative agreement that the province reached with Catholic and francophone teachers' unions, then pressured the rest of the unions to adopt.

The new law will ensure provincial trustees associations are represented at the main bargaining table, along with the government and unions, said Education Minister Liz Sandals. It would also require that all three parties ratify any central agreement.

If talks go south, the law also clarifies when the parties go to the Labour Relations Board and arbitration.

There will be a period of adjustment, Sandals said. The law should be in place before most of the existing agreements expire in August.

It will make the process very clear, rather than having it made up "on the fly" as in past years, the minister said.

"Everybody knows exactly how the process is going to work and how we settle disputes if the process isn't working," Sandals said.

Under the law, arbitrators can take into account such things as the economic situation in Ontario and the school board's ability to pay.

Sandals suggested that keeping costs down will again be a key issue for the Liberals -- who are facing an $11.3 billion deficit this year -- in the next round of bargaining.

Last time around, high school teachers withdrew from extracurricular activities in protest of the controversial law, which was repealed in January 2013.

But students could be deprived of those activities again, the Progressive Conservatives warned.

The bill wasn't amended so that withdrawing from extracurriculars would constitute strike action, which requires a vote by union members, they said.

"We're going into a very tough round of negotiations," said Opposition education critic Rob Leone.

"There's a huge deficit and the money that's been allocated to school boards to undergo this negotiation is very limited. The prospect for labour action is very high. We want to make sure that when that happens, the extracurricular activities are protected to the greatest extent possible."

The Elementary Teachers' Federation of Ontario, which represents 76,000 education workers, said it was happy that the bill was amended to limit the government's ability to control the central items under negotiation.

"Most importantly, the Act protects local bargaining and the right to strike at both provincial and local levels," the union said in a statement.

The New Democrats said they supported the bill to make sure that the Liberals respect the collective bargaining process this time around.

The government is doing damage control after throwing the education system in chaos two years ago, said NDP Leader Andrea Horwath.

"So this is the clean-up bill," she said. "They made a mess."