Mexican teachers’ on strike in Mexico leaving at least a million children without classes, in an effort to halt an education overhaul and disrupt coming federal midterm elections.

On Friday the Mexican government suspended indefinitely its planned teacher evaluations that were a cornerstone of the country’s education overhaul, in a decision ahead of midterm elections that dissident teacher groups threatened to boycott.

The evaluations for teachers had been scheduled for coming months. The decision followed months of agitation from union members, and sparked condemnation from opposition lawmakers and supporters of the law, who said it would gut the reform.

The Education Ministry didn’t explain its reasons for suspending the tests, except to say in a statement Friday that there were “new elements to be considered.”

Education Secretary Emilio Chuayffet announced the “indefinite suspension” of teacher evaluations in a brief message Friday night on his secretariat’s website. The message was later deleted.

Even with the concession from the Peña Nieto government, angry teachers shut down schools Monday in much of Oaxaca, Michoacán, Guerrero and Chiapas states, closing the doors on millions of pupils. The strike is to last until June 8.

The decision followed months of agitation from union members, and sparked condemnation from opposition lawmakers and supporters of the law, who said it would gut the reform.

Buoyed by the retreat, 10,000 teachers and opponents of what Peña Nieto has argued is his most important piece of legislation massed on the Paseo de la Reforma, one of the capital´s main boulevards, in an effort to kill off evaluations altogether.

In the World Economic Forum´s latest annual competitiveness survey, Mexico ranked 118th out of 144 countries in quality of primary education, behind many poorer countries, including Honduras, El Salvador, Bolivia, Bangladesh and Sierra Leone.

The government´s reasons for suspending the teacher evaluations have not been clearly explained. The Education Ministry said only that it had "new elements to consider" and declined to comment further when contacted on Monday.

In coming days, teachers say they will hold more strikes and will block the Mexico City airport and highways across southern Mexico.