The D.C. Tuition Assistance Grant, a unique federal initiative that allows city students to attend colleges and universities across the country at reduced rates, has opened up higher education to thousands, but rising costs now threaten to limit its reach, Mayor Anthony A. Williams testified yesterday at a congressional hearing.

The program, set to expire in 2005 unless Congress adopts a bill to extend it, has given 6,527 students grants totaling more than $63 million. Williams said more than half the recipients surveyed said they were the first members of their families to attend college.

The number of participants has steadily increased, to about 5,000 in 2004, and rising tuition rates are expected to increase the annual funding needed from $17 million to $25.6 million.

Williams said the number of D.C. high school graduates enrolling as freshmen in U.S. colleges rose from 1,750 in 1998 to 2,230 in 2002. The increase of more than 27 percent compared with average growth of 5 percent in states.

"No state in the union can make that claim," Williams said. "This unprecedented figure is due in large part, if not almost exclusively, I believe, to D.C. TAG."

The program's advocates laid out their case yesterday before the House Government Reform Committee. The hearing room was packed with supporters, including teachers, counselors and 50 college-bound students from the Washington Math Science Technology Public Charter High School.

"Every other city has a state to pay the costs of higher education opportunities, " said the committee chairman, Rep. Thomas M. Davis III (R-Va.), who, along with Del. Eleanor Holmes Norton (D-D.C.), introduced a bill to make the program permanent. "This was just an attempt to level the playing field. I think it succeeded, and in my opinion, the program ought to be enhanced."

Grants were awarded beginning in 2000, a year after Congress approved legislation.

After the hearing, LaRue Purry, 18, a Southeast Washington resident and a freshman studying computer science at the University of Alabama at Birmingham, praised the program.

"This program gave me the opportunity to get the education I always wanted, the education my family couldn't provide for me," Purry said. He said that his father and older brother are incarcerated and that his mother is chronically unemployed.

Under the program, D.C. high school graduates can attend participating colleges and universities across the country at in-state or discounted tuition rates.

Students who attend participating private schools -- historically black colleges and universities or private facilities in Maryland and Virginia -- can receive $2,500 a year, up to a lifetime total of $12,500.

At participating public colleges and universities, the federal government pays the difference between in-state and out-of-state tuition up to $10,000 a year or $50,000 over a lifetime.

This semester, for example, the University of Maryland is charging undergraduates $3,380 for in-state tuition and $8,717 for out-of-state tuition. At the University of Virginia, annual tuition is $6,150 for in-state students and $22,170 for out-of-state students.

The tuition assistance program has become a cornerstone of initiatives to stanch the flight of families from the District and to draw new middle-class residents.

Now its administrators are struggling to keep pace with enrollment and skyrocketing college tuition. If Congress does not increase funds available for grants by the fall of 2005, aid levels may be cut, grant duration may be reduced from five years to four, or new eligibility requirements may cut off grants to middle-class and wealthier families, city officials said.

Last year, the program awarded grants to 3,720 students at more than 300 schools.

Recently, the D.C. inspector general and D.C. Council member Phil Mendelson (D-At Large) questioned whether some of the federal grant money was improperly spent on trips taken by an administrative assistant.

Meanwhile, House Appropriations Committee spokesman John Scofield said yesterday that the District has not told the panel about an increase in costs.

"The program has enjoyed tremendous bipartisan support, but we are concerned about any cost increases," Scofield said. "This is going to be a really lean budget year, so funds are very scarce."

Williams rejected the idea of establishing need-based aid limits, saying states offer cheaper in-state tuition rates to all their residents. "The model of this program is the model of the states, where education is based on citizenship, not on income status," the mayor said.

Norton said congressional supporters want to ensure that the program is extended before tackling rising costs.

She said she is certain Congress will continue the program at $17 million a year.

Davis said he hopes to win renewal of the program this year but said there could be a battle over extra funding. "I hope we can get a little more. It's a tight budget year," he said.

Davis and Norton introduced the legislation creating the program after conferring with business and community leaders, including Washington Post Co. Chairman Donald E. Graham.