TORONTO -- Education Minister Liz Sandals says she is "perplexed" as to why high school teachers in Durham Region are on strike.

Talks at the local level with the Durham District School Board broke down over the weekend ahead of their legal strike date today, leaving schools in the region east of Toronto closed and 24,000 students out of class.

Central negotiations resumed today between Ontario high school teachers and the government after the Ontario Secondary School Teachers' Federation announced last week it had walked away from talks.

This is the first round of negotiations since the province brought in a new bargaining system, with both local and provincial talks.

Sandals stresses that the Durham strike is at the local level, though she says she hasn't heard a "coherent explanation" of what local issues prompted the walkout, so she is "mystified."

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.

Three years ago the Liberal government legislated contracts and wage freezes on the teachers, angering the unions.

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.