A showdown between the Bush administration and rural America threatens to undermine the White House’s efforts to raise standards.

Schools chiefs representing vast swathes of America want exemption from the No child left behind Act, contending the new education law is unworkable in rural areas.

The popular image of America is as the home of teeming metropolises like New York and Los Angeles, but unlike Britain, much of the country is sparsely populated.

Teachers at schools in Montana, Wyoming, Alaska, Nebraska, Maine and many other states typically do the work of several of their peers in urban schools, straddling whole science or humanities curricula in lessons.

“It’s absolutely necessary because of small student numbers and small school size,” explained Wayne Sanstead, schools chief of North Dakota, where more than three-quarters of schools have fewer than 75 pupils.

But new demands that staff be certified in each subject they teach has sparked mounting outcry from local officials, balking at the prospect of dismantling age-old training systems geared towards instilling general, multi-subject expertise, and asking veteran teachers to retrain.

The White House has been deluged with petitions for waivers from states which contend that the reforms are untenable. They fear they may hasten the exodus of their teachers to better-paying city schools. “We can’t understand the one-size-fits-all approach; you can’t put us all in the same mould,” said Mr Sanstead.

Another bone of contention is school choice, mandating low-performing schools to pay for students to transfer to adjoining ones with better test scores. Rural schools are often separated by hundreds of miles of rugged terrain.

Bush’s officials gave Alaska, America’s northern-most state, some leeway on this part of the legislation last month, after education secretary Rod Paige took a helicopter to trace the 164-mile trip across the Bering Sea some pupils there would have to take to switch schools.

However, officials have offered no relief from the law’s requirements for the mainland states so far.