As lawmakers begin the process of renewing the No Child Left Behind Act (NCLB), a report released June 7 by the Education Department (ED) is sure to fuel debate about whether the federal education law should be overhauled to make standards more uniform from state to state.

The federal government’s first-ever comparison of how states test for student progress in school shows large variations across the nation. For example, a reading score that rates a fourth-grader “proficient” in Mississippi would be a failing score in Massachusetts.

The study compared what it takes to be rated “proficient” on elementary- and

middle-school state reading and math tests to what it means to hit that mark on national tests. It found most of the scores that would label a student proficient on state tests don’t yield that grade on the national tests.

There also are huge differences in where states set their benchmarks. Massachusetts sets the proficiency score on its fourth-grade reading test at a point just below the proficiency mark on the national test. But a fourth-grader in Mississippi can be rated proficient with a state test score that is nearly 70 points lower. Proficiency is defined as working at the level expected for that grade.

ED’s report on the wide discrepancy in state proficiency standards casts the findings of another recent report in a new light. That report, released by the nonprofit Center on Education Policy (CEP) on June 5, indicated that students are doing better on state reading and math tests since NCLB was enacted five years ago, though the report said it’s too early to attribute these gains to the law itself.

Students made the most progress on elementary-school math tests, according to the CEP report, which focused on states where trend data are available. Some states have changed tests in recent years, making it impossible to compare year-to-year results.

Moderate to large gains were found in 37 of the 41 states with trend data on the percentage of kids hitting the proficient mark on elementary math tests. None of the states showed comparable declines.

A goal of NCLB is for all kids to be proficient in reading and math by 2014.

Another goal is to narrow achievement gaps between children from low-income families and wealthier ones and between minorities and white students. The CEP report found achievement gaps have narrowed since the law was passed.

Specifically, the study found that in 14 of 38 states with relevant trend data, gaps narrowed on the reading tests between black and white students at the elementary and secondary levels. No state reported a comparable widening of the gap.

In math, a dozen states showed a narrowing of the racial achievement gap at the elementary and secondary grade levels. Only Washington state showed a widening of that gap.

Results were generally similar for Hispanic and low-income groups, according to the report.

Just 13 states had enough data to examine whether the pace at which students improved has quickened since NCLB was enacted. In nine of those states, students improved at a greater rate after 2002 than before: Kansas, Kentucky, Louisiana, New Hampshire, New Jersey, New York, Pennsylvania, Washington, and Wyoming.

In the other four states–Delaware, Massachusetts, Oregon and Virginia,–gains were greater before 2002 than afterward. One possible explanation is that more students, such as those with disabilities or immigrants, were included in NCLB-era tests but not in the earlier ones, according to researchers.

Education Secretary Margaret Spellings said the CEP study shows NCLB is working, but the report itself doesn’t assign credit to the law for the improvements made. It notes that other state and local initiatives have taken place during the same period that might deserve some of the credit.

“You can’t tease out the effects of any one of the reform efforts, because they all overlap on one another,” said Jack Jennings, CEP president.

Also, as ED’s report shows, the rigor of tests varies widely from state to state, said Bruce Fuller, a professor of education and public policy at the University of California at Berkeley.

He said states generally set the proficiency bar low, because schools face tough consequences if their students do poorly on the tests. He also noted that some of the gains might reflect what teachers are focusing on in their classrooms.

“The teachers teach to the test, and that’s a rational response by classroom teachers under pressure to raise scores,” Fuller said.