WASHINGTON--Just a year after former Harvard president Derek C. Bok co-wrote a book championing the use of race in the university admissions process, two Harvard professors have released a survey which they say shows students believe diversity has had a positive impact on their education.

Gary A. Orfield and Dean K. Whitla, both professors at Harvard's Graduate School of Education, announced Wednesday the results of what they say is one of the first studies to directly link diversity to educational outcomes.

Orfield and Whitla hired the Gallup Organization to survey 1,820 students from the Harvard and University of Michigan law schools. Of those surveyed, about 90 percent of the students felt that diversity had a positive impact on their education.

"It was an educational process that affected everyone pretty deeply," said Orfield, who is co-director of the Civil Rights Project, the Harvard institute that sponsored the survey.

Nearly two-thirds of the respondents said that diversity improved class discussions, and roughly 62 percent said diversity clearly or moderately enhanced their ability to work more effectively and get along better with others.

But critics of the survey say that the questions of the impact of diversity on the students are vague.

"To say that most law students have benefited from diversity begs the question 'What is diversity?'" said Edward Blum, executive director of the Houston-based Campaign for a Colorblind America (CCBA), a non-profit organization that lobbies against racial preferences. "How do we know when we have achieved it?"

For the survey's purposes, Orfield and Whitla focused on racial and ethnic diversity.

Orfield contends that affirmative action in admissions is necessary in order to make up for past discrimination and to ensure an educated population.

"We still have a very unequal playing field out there, and in some ways it's becoming more unequal," Orfield said.

The survey results indicate that Orfield is not the only person who holds that belief. 80 percent of the survey's respondents support maintaining or strengthening existing minority admissions policies.

But the CCBA argues that such results are misleading, especially given the nature of the survey, which was conducted primarily over the telephone.

"Telephone surveys in matters of sexuality and matters of race are uniformly skewed," Blum said. "People respond to a race question much differently over the telephone than they do in private."

In addition, the organization says the questions were loaded to get the responses the surveyors desired.

"I think it's ironic that these questions were given to law students," said Marc Levin, executive director of CCBA. "Many of these questions, if they were presented in a courtroom, would be considered leading questions."