ATLIACA, Mexico - Easter vacation was over, but there wasn't a teacher in sight at the boarding school for indigenous children on the edge of this sunbaked southern Mexico hill town.
A 37-year-old cook who hadn't finished high school sat between two little girls on a concrete stoop outside the kitchen, peering at their dog-eared notebooks as they struggled with the alphabet and basic multiplication.
"I've got the children here. If there aren't any classes while they're here, I have to teach them," said the cook, who shared only her first name, Gudelia, for fear of retaliation from striking teachers.
A short drive away, teachers marched by the thousands through the streets of the state capital, some masked and brandishing metal bars and sticks in an escalating showdown over education reform that's become a key test of President Enrique Peña Nieto's sweeping project to reform Mexico's most dysfunctional institutions.
The fight is dominating headlines in Mexico and freezing progress on a national education reform that Peña Nieto hoped would build momentum toward more controversial changes.
Peña Nieto's first major legislative victory after taking office in December was a constitutional amendment eliminating Mexico's decades-old practice of buying and selling teaching jobs, and replacing it with a standardized national teaching test. That's heresy to a radical splinter union of elementary and high school teachers in Guerrero, one of the country's poorest and worst-educated states. The teachers claim the test is a plot to fire them en masse as a step toward privatizing education, although there is little evidence the government plans that.
Reform advocates say the dissidents simply fear losing control over the state education system and the income it provides, despite the need to reform a system that eats up more of the budget and produces worse results than virtually any other in the world's largest economies.
The 20,000-member group walked out more than a month ago, turning hundreds of thousands of children out of class. Then it launched an increasingly disruptive string of protests.
On Wednesday, the protesters won support from a wing of the armed vigilante groups that have multiplied across poor Mexican states in recent months. On Thursday, they blocked the main highway from Mexico City to Acapulco for at least the third time, backing up traffic for hours. On Friday, they shut down entrances to some of the biggest stores in the state capital.
After returning Mexico's former ruling party to power, Peña Nieto won international acclaim in his first five months by taking on some of the country's most powerful people. He jailed the head of the far-larger national teacher's union when she threatened to fight school reform.
Now the president finds himself facing unexpectedly tough resistance from rural teachers in straw hats and plastic sandals in his first direct conflict with the Mexican far left.
"If it spreads into other states, then it's a real problem. It means the government can't just plan on pushing the agenda from the top," said Federico Estevez, a political science professor at the Autonomous Technological Institute of Mexico.
The conflict is fueled by the importance of teaching jobs for the poor mountain and coastal villages where the dissident union is strongest.