Senate victory could pave the way for national subsidies for poor pupils in private schools, reports Jacqui Goddard.
Plans for America's first federal government-funded school voucher scheme have scraped through the House of Representatives by a single vote, setting the stage for bitter political confrontation as they approach the final hurdle of a vote in the Senate.
Republican leaders are accused of securing their victory by scheduling the vote on Tuesday of last week to clash with a televised Democratic presidential debate in Baltimore, Maryland.
Democrats are still threatening to derail the measure in the Senate where the Republicans' slim, two-vote majority makes the outcome too close to call.
Critics say the $10 million (pound;6.2m) pilot scheme, which would be launched in Washington DC next year and pay for at least 1,300 disadvantaged pupils to enrol at private schools, will drain money away from an ailing state system.
But the Bill's original sponsor, Congressman Jeff Flake of Arizona, said vouchers would provide a passport to a better education for pupils from poorer families.
"These scholarships will give DC children a chance to attend a school where they can succeed, while at the same time improving the schools by introducing competition," he said.
Under the scheme, disadvantaged families - for example, a family of four living on less than $34,000 (pound;21,250) - could apply for publicly-funded "opportunity scholarships" worth up to $7,500 per pupil per year.
The success or otherwise of vouchers in Washington DC, whose schools are the worst in the nation, will have huge implications across America.
Todd Ziebarth, policy analyst at the Education Commission of the States, a policy institute in Denver, Colorado, said: "The passing of this legislation is highly significant. It may give political cover for states to say: 'Look, the federal government is going down this road, so we should consider it.' It may open the door to states enacting more programmes and open the door to the federal government expanding this in future years."
Race is an important issue. A campaign group called DC Parents United for School Choice says that, as most of the capital's disadvantaged children are black, blocking vouchers will deny them the chance of a better future.
It has launched hard-hitting television advertisements singling out key Democratic opponents, among them Senator Edward Kennedy of Massachusetts.
In the advertisements, the group's director, Virginia Walden-Ford, recalls life as a child growing up in Arkansas during segregation in the 1960s, when state governor George Wallace famously stood in the door of a school to prevent black people from entering. She then recalls how the late Senator Robert Kennedy came to the rescue of the civil rights movement.
"Forty years later in Washington DC, poor black children face the worst school system in the country and thousands of moms are asking: 'Who's going to save us?'" said Mrs Walden-Ford. "There's a plan in Congress that will save these children. But when I learned one senator threatens to stop this from happening, I cry. Because his name is Kennedy."