Texas appears likely to change its law guaranteeing the top 10 percent of graduates of state high schools admission to the public college of their choice -- though isn't clear yet just how extensive the changes might be.

The state House of Representatives voted Thursday to rein in the law by allowing any public institution to cap at 50 percent the proportion of its freshmen that it must set aside for students in the top 10 percent of their high school classes. But the Texas Senate rejected any such cap in passing its much gentler modification of the 10-percent law last week, setting up a fight over a compromise in the two remaining weeks of the legislative session, with the outcome uncertain.

Texas adopted the class rank law in 1997, in the wake of a federal appeals court ruling, in a case known as Hopwood v. Texas, that restricted colleges from considering race as a factor in admissions. Sponsors of the law hoped that by ensuring college admission to top graduates of the many segregated high schools that are dominated by black and Hispanic students, it would minimize the ban's impact on minority college enrollments.

Supporters and critics of the law, which was imitated to varying degrees in states such as California and Florida, tend to cite differing statistics to argue its success or failure. Opponents -- noting that more than 70 percent of freshmen at the University of Texas at Austin were admitted because they finished in the top 10 percent of their high school classes, and that those students had a lower average SAT score than the rest of the freshmen -- complain that highly qualified students at very competitive high schools are being shut out of top colleges. They have argued for repealing or at least limiting the reach of the law.

Backers of the 10-percent law, citing statistics showing that the representation of minority students at public colleges has increased somewhat but not significantly under the measure, suggest that if anything, it should be extended or strengthened.

Texas's flagship Austin campus has taken the most visible stand in the debate. Its officials say that they continue to support the overall concept of the law, but that having to admit such a large proportion of their students only on the basis of class rank limits their ability to craft a diverse class. That is especially true, they say, now that the U.S. Supreme Court, in its decision last year in the University of Michigan case, has given colleges more latitude to consider race as one factor in admitting students.

"Students are not one-dimensional," President Larry R. Faulkner said in a speech last fall. "It is unhealthy for Texas and for this university to admit such a large percentage on a single criterion and to ignore everything else in an applicant's record." The university has urged lawmakers to let individual institutions limit the proportion of their freshman classes that were set aside for the 10-percenters.

As the legislative session has unfolded over the last few months, lawmakers considered a slew of measures this year that would have changed the 10-percent law in some way, including some that would end it entirely and others that would modify it in ways large and small.

In the Texas Senate last week, lawmakers approved a measure (SB 333) that would make students eligible for admission under the 10-percent plan only if they took the state's recommended or advanced curriculum while in high school. But senators specifically discussed and decided not to vote on a proposal to cap the percentage of its students a college must admit under the law. Sen. Royce West, a Democrat who sponsored the Senate bill, vigorously opposed such a cap.

The bill (HB 2330) that emerged Thursday in the House, which was sponsored by Rep. Geanie Morrison, a Republican, would give UT-Austin the cap that it is seeking. "This is a compromise of all bills (on the subject) to keep the positive part of the top 10 percent law and its beneficial aspects, but it addresses the unintentional consequences that have taken place," Morrison said on the House floor Wednesday.

The House bill now shifts to the Senate, and if the Senate passes its own version of that legislation, House and Senate lawmakers will work to craft a compromise between the two measures. If they can't reach one between now and May 31, when the legislative session ends, the 10-percent law is likely to remain intact -- at least until next year's session.