One in a series of occasional articles on the people affected by the No Child Left Behind law.

Robert G. Smith, superintendent of the Arlington County schools, has been on a winning streak.

When he took the job in 1997, experts wondered whether the county's many low-income students with limited English skills could handle the new Virginia standardized tests. But he and his school board gave teachers time and money to prepare, and by last year, all 30 Arlington schools had reached the state's testing benchmarks or were close to doing so.

Now, like many other successful superintendents, Smith has to start over. The federal No Child Left Behind Act, which took effect in July, has imposed a new set of test score targets and deadlines. The law is so complicated that interpretations seem to change every month, and Smith has had to submit a 92-page application just for the privilege of having his assessment system knocked askew by the U.S. Department of Education.

"I am positive about establishing clear standards. I am positive about assessing clearly what we hope to accomplish. I am also positive about disaggregating data and making sure all of our children are doing well," he said. "But like so many other things, the devil is in the details."

The No Child Left Behind law is the latest version of a two-decade-old effort to ensure that all U.S. students learn to read, write and do mathematics well enough to succeed on the job or in college. It began in southern states, where bad schools were hurting the local economies. Smith is familiar with that history because he spent 16 years as a school administrator in Spring, Tex., watching a succession of governors, including George W. Bush, insist on better accounting of public school achievement.

Smith acknowledges that the national effort has improved education in some of the country's worst school districts, but he worries that it may have less beneficial effects in districts, such as Arlington, that are already doing a good job.

When measured by per-pupil spending, test score gains and high school course quality, Arlington is one of the best districts in the country. One of its schools with a majority of low-income students, Barcroft Elementary, has won national attention for surprisingly high test scores.

Smith said he has been trying to decipher the new law and determine what Arlington must do to meet its standards. "Our major initiative initially with No Child Left Behind was to try to figure out what it was doing to us," he said.

He has budgeted an extra $150,000 to collect data on the college majors and other credentials of his approximately 2,000 classroom teachers so he can determine whether any are teaching subjects they do not entirely understand, a no-no under the federal law. He also is investigating the effect of the law on his 343 instructional assistants, many of whom are supposed to have at least two years of college education, or the equivalent, under No Child Left Behind. He has budgeted $153,000 to help the assistants pay for any extra college courses they might need.

For the first time, he has also had to notify all parents of children receiving special instruction in English, even down to kindergarten level, that they have been designated for extra help. "I think we communicated that before," he said, "but not to the extent we do now."

Arlington will lose about $200,000 a year because of a change in the way grants are awarded for helping children from non-English-speaking families, he said. The increase in overall federal funding for education under No Child Left Behind will make up for that loss, but not by much.

Now his focus is on the new federal 95 percent rule, which requires that local districts test at least 95 percent of students in any of the subgroups identified in the law -- non-Hispanic whites, blacks, Hispanics, Asian/Pacific Islanders, Native Americans, students with limited English, special education students and low-income students.

A particularly important change for Arlington, where 41 percent of the students come from non-English-speaking households, is a rule that such students must be tested within three years of their arrival in the school system. Under the old state rules, the district had five years to prepare such students before giving them the tests, and Smith said that the new tests may not be a valid measure of what the students can do.

Several of his schools, he said, will have trouble reaching the new federal standards and making the "adequate yearly progress" that will determine if they get the dreaded "needs improvement" label or not. Schools so designated will be required to provide extra tutoring for students who want it and transportation to other schools for families that demand it.

Continued failure to meet the standards could lead to replacement of school staffs and other drastic measures.

Another new rule, however, may save some Arlington schools. Like other states, Virginia has asked that yearly progress not be calculated for racial or other subgroups of less than 50 members at any school. At least four north Arlington elementary schools -- Jamestown, Nottingham, Tuckahoe and Taylor -- are unlikely to have that many black, Hispanic, low-income or special education students, Smith said.

But even those schools will have to show steady improvement for all of their students on standardized tests, a requirement that Smith fears will lead to less imaginative teaching. The federal law, he said, encourages "a narrow gauge approach to education where we reduce that which is taught to that which is tested. That is the real concern."

First, Arlington County Superintendent Robert G. Smith says, the district had to "figure out what [the new law] was doing to us."