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The No Child Left Behind law was supposed to level the playing field, promising students an equal education no matter where they live or their background. From state to state, however, huge differences remain in what students are expected to know and learn.

Each state sets its own standards for subjects such as reading and math, then tests to see whether students meet those benchmarks. It's a practice under increasing scrutiny as prepares to review the five-year-old law.

"Fourth-grade kids in the District of Columbia are learning different math from kids across the (Potomac) river in Virginia. It's crazy. Math is math," said Michael Petrilli, vice president for policy at the Thomas Fordham Foundation, a Washington-based education reform group.

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The solution, say Petrilli and other advocates, means standards of learning that are uniform nationwide.

Republicans generally have opposed national standards. GOP lawmakers say state and local officials know what is best for their students and as the primary funders of elementary and secondary education, should have primary say in running schools.

Education Secretary Margaret Spellings has opposed national standards but recently indicated she would consider voluntary ones. Spellings said she would have strong reservations, however, about proposals that would free states from the No Child Left Behind law's requirements as a reward for raising standards.

Many Democrats, along with education reform and business groups, say a patchwork of standards is inefficient. They also say students in states with low standards will have trouble competing in the global economy. Many other industrial nations have more stringent standards than those in the U.S.

There are signs states are wrestling with the problem. Some are talking about sharing tests and looking at benchmarks that would identify the skills U.S. students should have when they finish high school.

Advocates of national standards say the No Child Left Behind law is encouraging states to set low standards so schools can avoid consequences that come with missing annual progress goals.

Schools that miss those targets must take steps such as paying for tutoring or overhauling staffs. All students have to be proficient, which generally means working at grade level, in reading and math by 2014.

At least one state, Missouri, lowered its standards after the federal law went into effect.

Gene Wilhoit, executive director of the Council of Chief State School Officers, said it is understandable that some states would set low standards. "They're trying to make sense out of this. They're trying to survive," he said.

Wilhoit said, however, that is seen as unfair that states with high standards are treated the same as those with lower standards. He said states willing to raise their standards to a high, possibly uniform, level should be given regulatory relief and financial incentives.

Supporters of national standards point to the vast differences between student performance on state tests compared with a rigorous national one as evidence states are using weak standards.

A study by the Washington-based children's advocacy group EdTrust showed 89 percent of fourth-graders in Mississippi were deemed proficient or better in reading on recent state tests. Meanwhile, only 18 percent reached that level on the National Assessment of Educational Progress — the gold-standard of scholastic achievement in the United States.

In Oklahoma, 75 percent of fourth-graders were proficient or better in math on the state test. On the federal test, 29 percent met that standard.

In Massachusetts — a state with relatively high standards — the gap is narrower. Fifty percent of fourth graders were proficient in reading on state tests, compared with 44 percent on the national test.

Massachusetts Democratic Sen. Edward Kennedy, chairman of the committee overseeing education issues, has proposed legislation generally encouraging states to raise their standards to a consistent level, as has Sen. Chris Dodd, D-Conn.

Dodd's legislation won the endorsement of the National Education Association, the largest teacher's union.

"We know that we need to take a look at the rigor and the wide diversity and range of content standards," NEA lobbyist Kim Anderson said.

One bit of evidence that uniform standards are effective comes from schools run by the Defense Department for military families.

Student scores at those schools, which operate outside the No Child Left Behind law but which have uniform standards, are higher on the national assessment than scores of other students, according to Vanderbilt University researcher Claire Smrekar.

She said there are many reasons for that trend but that uniform standards at the Defense Department schools play a role. "I would say they provide clarity and consistency within the system," she said.

Among educators, there is a concern national standards would become outdated and that changing them would be difficult and bureaucratic.

Brenda Dietrich, a superintendent in the Topeka, Kan., area, said she has not formed an opinion on national standards, but does see a logic to them.

"If we're all going to be held to a standard, it certainly would be nice if it were the same standard," Dietrich said.

That is probably going to be the winning argument, says Michael Dannenberg, who directs education policy at the Washington-based New America Foundation, which recently held a forum on national standards. "My view is that the country is on an inexorable march toward national standards, and the question is not if but when and how," he said.

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