Eight states are giving serious consideration to new laws which would enable voucher experiments to take place, says Connie Koprowicz, who works on education policy at the National Conference of State Legislatures in Denver. Pennsylvania is talking about a statewide voucher scheme for low-income parents.
"Since the elections last November there has been a significant increase in interest in choice plans, particularly the kind of plan that exists in Milwaukee, which has targeted low-income students and is aimed at central city schools," says Paul Peterson, a professor of government at Harvard University.
But the battle for the schemes is far from over. Ballot initiatives to give parents vouchers to "spend" at the publicly-funded or private school of their choice have been roundly defeated in Oregon, California and Colorado. But the political climate may be changing.
Today's Republican governors, particularly those who were elected on pro-voucher platforms, believe they have a mandate for reform. And they are looking to Milwaukee, Wisconsin, home of the only voucher scheme in which parents receive state money to spend at private schools of their choice, as their blueprint.
Introduced four years ago in the teeth of considerable opposition, including a court challenge, the Milwaukee experiment enables up to 1,500 children in the largest city in the state to attend private, nondenominational schools. Their parents receive a voucher worth $3,200 (Pounds 2,100).
The brainchild of Polly Williams, a black Democrat representative, the scheme is popular with local parents and businesses. The number of pupils attending private schools by this method has been increasing every year, and supporters are hoping to expand its remit to religious schools.
However, education experts have not been so enthusiastic. Professor Peterson has been trying to evaluate the scheme for months, but says he has been frustrated by a lack of data. A study of Milwaukee's scheme has been conducted by a University of Wisconsin professor, whose reports have not been made public.
Peterson says the Wisconsin professor's report does not conform to today's standards.
"He doesn't take account of a sufficient number of background characteristics in students," says Peterson. "He reports finding that students in choice schools don't learn any more than students in public schools. But I find that the choice school students have disadvantages in their background characteristics that make them different from students in public schools".
All of which makes it difficult for states emulating Milwaukee to argue that its experiment can be shown to have pushed up standards.
The eight states with voucher legislation in the pipeline are Texas, Illinois, Pennsylvania, Arizona, Alaska, Florida, Kansas and Ohio, according to Ms Koprowicz.
Ohio is thought to have the strongest chance of passing a limited voucher scheme - one targeted at a number of poor children in specific inner city areas. Pennsylvania's plan for a statewide programme is the most ambitious, and is expected to meet intense opposition from teachers' unions.
The idea is to phase it in over three years and make it available to all families earning less than $25,000 a year.
The rationale advanced for vouchers in American schools is twofold: that poor families in inner cities have no options and vouchers would give them some; and that schools in such areas would be forced to change for the better once vouchers were introduced.
The trouble is that no state has introduced vouchers on a big enough scale to test these hypotheses. "Milwaukee is too small," says Ms Koprowicz. "Until someone is willing to give a fuller plan a chance, we don't know. It's all speculation"
Behind the movements for reform - the toying with vouchers and introduction of charter schools (like opt-out schools in Britain) - lies a real, and bipart-isan, concern about the state of education in American cities. "It's an effort to break the bureaucracy and to make change," says Koprowicz. "The disagreement is about how to do that."