The Manassas City School Board, which oversees a small system with a large concentration of students who have limited English, this week reluctantly abandoned an effort to defy a controversial federal rule for testing those students.

On Tuesday, the board agreed to comply with the mandate of the No Child Left Behind law to give grade-level reading tests to about 350 elementary- and middle-school students who are not yet fluent in English. Previously, the board had considered resisting the rule through a resolution similar to those adopted recently by school boards in Fairfax and Arlington counties.

Manassas officials said they were swayed by a federal threat to cut off aid for disadvantaged students, a loss that could have been nearly $700,000 in the next school year, according to a U.S. Education Department letter made public yesterday.

"We are being blackmailed by the federal government," Manassas School Board member Curtis W. Wunderly said. Like many other Virginia education officials, Wunderly said that students should not be forced to take tests they can't understand and are all but certain to fail.

U.S. Education Department spokesman Chad Colby replied that the testing is necessary to help teachers identify the academic needs of students with limited English. Most school systems across the country, federal officials say, are following the law.

The action in Manassas was notable because about 35 percent of the estimated 6,500 students in the city's public schools have limited English proficiency. Only Harrisonburg, in the Shenandoah Valley, has a higher percentage of limited-English students among Virginia public school systems, state data show.

A letter from U.S. Deputy Education Secretary Raymond Simon, released by Virginia officials, spelled out how much federal aid for disadvantaged students school systems might lose if they fail to comply with the law: about $2.6 million in Arlington; about $3.1 million in Alexandria; about $1.3 million in Loudoun County; about $6 million in Prince William County; and about $17.5 million in Fairfax County. So far, only Fairfax and Arlington have declared their intention to resist the federal rule. Prince William has said it will reluctantly comply. Loudoun and Alexandria have not taken action.