April 13, 2005 | By GREG WINTER | New York Times

The academic growth that students experience in a given school year has apparently slowed since the passage of No Child Left Behind, the education law that was intended to achieve just the opposite, a new study has found.

In both reading and math, the study determined, test scores have gone up somewhat, as each class of students outdoes its predecessors. But within grades, students have made less academic progress during the school year than they did before No Child Left Behind went into effect in 2002, the researchers said.

That finding casts doubt on whether schools can meet the law's mandate that all students be academically proficient by 2014. In fact, to realize the goal of universal proficiency, the study said, students will have to make as much as three times the progress they are currently making.

The study was conducted by the Northwest Evaluation Association, which develops tests for about 1,500 school districts in 43 states. To complete it, the group drew upon its test data for more than 320,000 students in 23 states, a sample that it calls "broad but not nationally representative," in part because the biggest cities, not being Northwest clients, were not included.

One of the more ominous findings, the researchers said, is that the achievement gap between white and nonwhite students could soon widen. Closing the gap is one of the driving principles of the law, and so far states say they have made strides toward shrinking it.

But minority students with the same test scores as their white counterparts at the beginning of the school year ended up falling behind by the end of it, the study found. Both groups made academic progress, but the minority students did not make as much, it concluded, an outcome suggesting that the gaps in achievement will worsen.

"Right now it's kind of a hidden effect that we would expect to see expressed in the next couple of years," said Gage Kingsbury, Northwest's director of research. "At that point, I think people will be disappointed with what N.C.L.B. has done."

The findings diverge from those of other recent studies, including a survey last month by the Center on Education Policy, a research group. It found that a significant majority of state education officials reported widespread academic progress and a narrowing of the achievement gap.

"This new study should give everybody pause before they run off and say, 'We're marching to victory,' " said Jack Jennings, the center's president. "Maybe we're not."

Kerri Briggs, a senior policy analyst at the Education Department, said the Northwest study had both encouraging and worrisome aspects, but added that she would have to examine it more closely before passing judgment.

Some critics speculated that because the study lacked data from big cities, which have large populations of minority students and have posted significant gains on test scores in recent years, it might have overstated or mischaracterized what was happening with the achievement gap.

"It's hard to know how much you can extrapolate from this study," said Ross Wiener, policy director for the Education Trust, which released its own report in January showing mixed results on student performance and achievement gaps. "I don't think you want to make generalizations about what's going on nationwide."

Still, the Northwest study tracked student performance at a level that others did not, a factor that may help explain why some of its findings appear unorthodox. Rather than relying on test scores at just one point in the year, the Northwest study looked at how students fared in the fall and then again in the spring, in an effort to see how much they had learned during the year.

With this approach, Northwest found that test scores on its exams did, in fact, go up from one year to the next under No Child Left Behind, typically by less than a point. The reason successive classes appear to do a little better than those before them may stem from the fact that younger students have grown up during a time of more regular testing than their immediate predecessors, the researchers said, and are therefore higher achievers.

But rising test scores tend to mask how much progress individual students make as they travel through school, the researchers found. Since No Child Left Behind, that individual growth has slowed, possibly because teachers feel compelled to spend the bulk of their time making sure students who are near proficiency make it over the hurdle.

The practice may leave teachers with less time to focus on students who are either far below or far above the proficiency mark, the researchers said, making it less likely for the whole class to move forward as rapidly as before No Child Left Behind set the agenda.