TORONTO -- High school teachers in one Toronto-area board hit the picket lines Monday leaving 24,000 students out of class and the education minister "perplexed."

The strike -- the first by Ontario teachers since the Liberals came to power more than a decade ago -- followed the breakdown of talks at the local level with the Durham District School Board over the weekend.

It came the same day as the Ontario Secondary School Teachers' Federation resumed talks with the province after walking away from the negotiations last week.

This is the first round of negotiations since the province brought in a new bargaining system, with both local and provincial talks. Monetary issues are discussed at the central table and Sandals said she doesn't understand what drove Durham high school teachers to strike.

"Quite frankly, I've been very perplexed as to why there is a strike in Durham because I haven't heard a coherent explanation as to what the local issues are that have prompted a local strike," she said.

Sandals would not comment on a published report that suggested the talks broke down over the renegotiation of caps on class sizes.

The OSSTF has threatened strikes at six other school boards. Meanwhile, the Elementary Teachers' Federation of Ontario has asked for a "no board report," signalling that talks with the province are at an impasse, which will put the union in a legal strike position 17 days after the report is issued.

Sandals said she does not believe this is a return to the labour unrest that permeated the education sector while the Progressive Conservatives were in power.

"The whole point here is that we have indicated our willingness to negotiate, which was never something that you heard from (former PC Premier) Mike Harris," she said.

Durham's strike is "technically" not the first since the Liberals came to power in 2003, Sandals said, noting there were rotating one-day strikes three years ago when the unions were angered by the government's decision to legislate contracts and wage freezes on the teachers.

The relationship has since slowly improved but unhappiness is brewing once again as the Liberals try to eliminate a $10.9-billion budget deficit through measures that include "net zero" increases in contract negotiations, though the unions say there are outstanding issues other than wages.

Both opposition parties said the minister of education was blaming the local school board for problems that originate at the provincial level. This is the bargaining process the Liberals put in place, said NDP Leader Andrea Horwath.

Progressive Conservative critic Garfield Dunlop said the problem can be traced back to fiscal mismanagement.

"(Sandals) starts blaming the local school boards for the negotiations that are taking place," he said. "The reality is they're cash strapped because all the funding comes from the Ministry of Education."