An unsuccessful school board candidate filed a federal lawsuit Monday alleging that the Irving school district's system of at-large elections violates the law because it denies representation to Hispanics.

Manuel Benavidez, a Mexican-American who twice ran unsuccessfully for the Irving school board, is the named plaintiff in the suit, which was filed by attorneys for the Dallas firm Bickel & Brewer.

The named defendants are Irving ISD and its seven elected trustees.

Mr. Benavidez filed a similar suit in November against the Irving City Council's at-large election system. He could not be reached for comment Monday.

The suit asks the federal court to find that the at-large system of elections violates the Voting Rights Act of 1965. They ask that the school district develop a new single-member district system of electing representatives from individual districts carved out within district boundaries.

No Hispanics serve as school trustees in Irving ISD, whose officials estimate that 67 percent of students are Hispanic. About 42 percent of the city's residents are Hispanic, according to 2006 Census Bureau reports.

"The voting system puts the election of all school board members in the hands of the white majority," attorney Bill Brewer said. "It doesn't give ways for the significant Hispanic majority to have a fair opportunity for representation."

In 2000, voters elected Ruben Franco the school district's first and only Hispanic trustee. He served two three-year terms.

The school board was all white until this spring, when voters elected two African-American trustees, Nancy Jones and A.D. Jenkins. Two Hispanics ran against them, Stacey Ponce and Jorge Chac II. Ms. Ponce received about 17 percent of the vote and Mr. Chac, 18 percent.

Jerry Christian, Irving school board president, said the election of two black candidates shows that minorities can be elected if they are qualified.

"I don't think the election system's been proven to be unfair yet," he said. "We had two minorities that were elected this time who were individuals who had been involved in the school district for some time."

Others argue that white Irving business leaders often handpick who runs for office. Roland Medina, who is Hispanic, ran unsuccessfully twice for the City Council and supports both lawsuits in Irving.

"Without redistricting it's going to be very hard for a Hispanic ever to win," he said. "The city is long overdue on it. It's something they should have taken action on a long time ago."

School district attorney James Deatherage said he had not seen the lawsuit and did not want to comment.

"I don't know what the numbers will ultimately prove," he said.