Giant poster boards filled with data from standardized tests dominate the courtroom where attorneys for some of the poorest school districts in South Carolina are suing the state legislature for billions of dollars in education funds.

Rocking gently back-and-forth on his black leather chair, Circuit Judge Thomas W. Cooper Jr. can instantly compare student achievement levels in the predominantly black rural districts with test results from affluent suburbs nearby. A computer database provides him with detailed information on such matters as comparative teacher salaries, SAT scores and the number of students who qualify for free lunches.

The scene in the South Carolina courtroom has become common across the United States as lawyers use data generated by the drive for higher standards in education as the basis for class-action lawsuits seeking more funding for poorer school districts. According to experts who track the lawsuits, half the states in the country are now involved in litigation over education funding.

Similar lawsuits arguing for education equity between rich and poor districts were filed frequently in the 1980s. The more recent lawsuits, which seek sufficient funding for poor districts rather than parity with affluent ones, have been fueled, in part, by the Bush administration's No Child Left Behind initiative, which is designed to make every child in the country proficient in math and reading by 2014. Many poor school districts that fail to meet the targets established by the law have gone to court to argue that they lack the resources to compete with their richer neighbors.

These "educational adequacy" complaints have largely replaced desegregation lawsuits as the focus of legal efforts to ensure equality of opportunity between different social and ethnic groups. As federal courts stepped back from ordering school districts to use remedies such as busing to promote integration during the 1990s, local courts began examining whether state governments were living up to their constitutional responsibilities to meet the educational needs of their students.

"We don't have the money to employ and retain high-quality teachers," said Everette M. Dean, superintendent of Marion 7, one of eight South Carolina school districts involved in the lawsuit. "Our students aren't being given the opportunity to attain an adequate education."

Photographs submitted to the court by Marion 7 show schools with leaking roofs, decrepit wooden buildings, unpaved parking lots and makeshift science labs. Dean compares his district with neighboring Horry County, which includes the resort community of Myrtle Beach and can pay $10,000 bonuses to good teachers. By contrast, he said, Marion 7 can afford supplements of only about $300.

In recent years, judges have sided with the plaintiffs in about 70 percent of the adequacy lawsuits, ordering states to come up with extra money, said Steven Smith, an education analyst at the National Conference of State Legislatures. He predicted that the number of lawsuits is likely to rise as "more and more schools" fail to meet the goals of No Child Left Behind and state school accountability laws.

"Plaintiff organizations see the [No Child Left Behind] data as good ammunition to use in court," he said.

The adequacy lawsuits have been made possible by clauses in most state constitutions promising to provide a "basic" or "adequate" education. All but five states have witnessed some kind of legal battle over what constitutes an "adequate" education, and some states are gearing up for their second or third lawsuit.

"From our point of view, testing has been very helpful in pinpointing the problem, and showing exactly which kids are not making the grade," said Michael A. Rebell, the chief litigator for the Campaign for Fiscal Equity, which won a 10-year legal battle against the state of New York last year.

Over the past few months, plaintiffs have filed school funding lawsuits in states such as Missouri, Nebraska, Kentucky and Louisiana. Cases are ongoing in South Carolina, Massachusetts, Montana and Kansas. In the Washington area, a Maryland lawsuit was put on hold in 2002 after the state agreed to an independent panel's recommendation to find an extra $1.3 billion a year for needy districts by 2008. Plaintiff groups are considering filing suit in Virginia. The District's lack of a constitution has so far made it immune from the lawsuits.

Whether increased funding for poor school districts leads to improved student performance is debated. Alfred Lindseth, a Georgia lawyer who has represented the defendants in several adequacy cases, points to New Jersey, where, he says, academic performance has generally remained flat despite a sharp increase in funding over the past four years.

"If the money is spent wisely, you can get remarkable results," said Molly A. Hunter, director of legal research for the Campaign for Fiscal Equity. She argues that increased funding has resulted in improved performance among at-risk children in Kentucky and Vermont. She also points to improved performance in lower grades in New Jersey.

Critics argue that the lawsuits are diverting attention from other causes of student underachievement, such as lack of parental support and inefficient management techniques used by small rural school districts. In addition, they say, the courts are usurping powers that have traditionally been vested in state legislatures.

"It's up to legislatures to decide whether a state education system should be basic or world-class," Lindseth said. "If voters want to spend money on a world-class education system, that's great. But that's a decision for them, not for some judge, to make."

In several states, the funding lawsuits have led to a test of strength between the courts and state legislatures, with lawmakers either refusing to implement court orders on adequate funding or dragging their feet. Last month, a judge in Kansas threatened to close down the state's school system after the legislature took no action on his order to increase funding for poor schools. The case is now before the state Supreme Court.

"It's become like a poker game," said Smith, the education analyst. "Neither side will back down."

In Manning, the legal battle has come full circle. After World War II, poor black farmers went to court to ask for a school bus for their children, a case that was later overtaken by demands for complete desegregation of the school system that culminated in the landmark Brown v. Board of Education decision of 1954. Today, lawyers representing predominantly black school districts are back in court, seeking not integration but sufficient educational opportunity.

"We are showing that our school districts have the least experienced teachers," said Steve Morrison, the lead attorney for the eight heavily minority school districts that have joined the lawsuit. "Most teachers will jump to a different school district if they are offered an extra $5,000."

Lawyers for the South Carolina legislature argue that the state already has a wealth distribution policy that favors poorer school districts. "It's a myth that the poor districts are spending less money on education than the rich districts," said defense attorney Bobby Stepp, citing figures that show that Marion 7 spends at least $1,500 more per pupil than Horry County does.

Morrison counters that "per-pupil spending is a false standard," arguing that rural districts such as Marion 7 have larger numbers of at-risk students than their suburban neighbors and do not benefit from economies of scale.

How much it will cost to provide an "adequate education" in South Carolina and other states that have become the subject of lawsuits is far from clear. In New York, the Court of Appeals has established a July 31 deadline for the state to respond to plaintiff demands for a $9.5 billion increase in the education budget every year for the next four years, a 30 percent increase in funding.

"It's a huge amount of money," acknowledged Rebell, the lead attorney for the plaintiffs. "But there is a huge problem that needs to be solved. We are talking about a school system in which 40 percent of the kids drop out before they graduate."