In one of the biggest challenges yet to the way teachers are paid in the US, staff in Texas and Denver, Colorado, are to be offered “merit pay” that will reward them for exam results and working in tough schools and hard-to-fill subject areas.

Earlier this month, Texas governor Rick Perry announced the second-largest US state’s first performance-based pay scheme. He pledged $10 million (Pounds 5.42m) to give the highest-performing staff at 100 poor schools with the biggest test score gains a share of 100 $100,000 bonuses.

Mr Perry said he would seek a further $25m to extend the scheme to another 250 schools.

Meanwhile, in a landmark election in Denver, also earlier this month, voters approved a radical new salary scale, to be paid for by local tax increases. The new scale rejects the usual wage rises on the grounds of seniority and qualifications and instead links pay to test scores, performance evaluations, professional development, and work in the neediest schools and subjects.

The $25m merit pay scheme, piloted over the last year, is the most comprehensive yet embraced by a US city.

School chiefs in Houston, Texas, plan to announce final details of a proposed $14.5m plan to offer bonuses based on test scores to teachers next month.

The developments add to growing political momentum behind performance-based pay for US staff. More than 20 state governors have flagged it as an education reform priority this year, said Allan Odden, University of Wisconsin education professor.

“Among policy analysts, the consensus is that simply increasing pay isn’t going to get you better teachers,” he said.

In one of the most ambitious proposals to date, Massachusetts governor Mitt Romney called in September for an annual $65m bonus package, targeting instructors teaching advanced courses and short-staffed subjects, and those whose students’ results show marked gains.

But the movement faces vociferous opposition from a great many teachers “It’s a fad of the moment, a simplistic answer to a complex problem,” said Gayle Fallon, president of the Houston Federation of Teachers.

Many of the new plans are too obsessed with test scores, encouraging rote drilling rather than expansive teaching, she said, and measure teachers on factors beyond their control, such as the variability of students.

“We don’t have a randomised sample of kids,” she said.

Professor Odden said there was a clash between efforts to “create a more performance-oriented culture and a system where the focus has been on equity and process”.