A new study on affirmative action that says racial preferences used in law school admissions have a negative effect is coming under fire.

The study, written by UCLA law professor Rick Sander (search), says unprepared African-American students have difficulties succeeding in elite law schools and many end up dropping out. It also says that those who do graduate are four times less likely than white students to pass the bar exam on the first try.

"You're much more likely to graduate and pass the bar ... even more likely to get a job if you're in the middle of the class at a somewhat lower school," said Sander.

Critics say the study ignores the positive impact that affirmative action has among black students who are pursuing a career in law.

Former O.J. Simpson prosecutor Chris Darden (search) said many black students struggle initially but later end up learning more and becoming better lawyers.

"Some young man, some young woman ... might find his way to one of the premier law schools in the country ... and perhaps find his way to the Supreme Court," said Darden.

Sander said the real factor involved is not racial but preferences of any kind and that there's no upside to getting thrown in over your head if you aren't prepared to swim.

Click in the video box above to watch a report by FOX News' Trace Gallagher.