Professors have complained for years about the phenomenon known as grade inflation: the pressure to award a student an A for work that is really worth only a B. Now Princeton has become the first elite university to take drastic action to reverse the trend.

Princeton professors voted this week by a 2-1 margin to slash the number of A-plus, A and A-minus grades they award to students by about 25 percent, beginning next fall. The new policy is aimed at restoring the grading standards of the late 1980s, when an A signified "excellent" or "exceptional" work.

"We want to do a more effective job at giving our students finely calibrated feedback, so they know the difference between outstanding work and good work," said the dean of the college, Nancy Malkiel, who has conducted a five-year campaign to raise grading standards at Princeton.

Professors at several other Ivy League universities said Princeton's action is likely to reignite a nationwide debate on how to combat grade inflation. "It's definitely a step in the right direction," said Harvard government professor Harvey C. Mansfield, who would like to reduce the percentage of A's awarded by the nation's oldest university from about 50 percent to about 20 percent.

Although grade inflation has attracted growing attention in recent years, relatively little has been done to combat the phenomenon, and much of what has been done has proved ineffective. The number of A's awarded at Princeton and other universities has continued to creep up. The grade that used to be known as the "Gentleman's C," for acceptable but undistinguished work, is on the road to extinction.

Once a symbol of academic perfection, A's have become the most popular grade at many universities. More than 45 percent of the grades awarded at Princeton from 1997 to 2002 were A's, compared with just 30 percent a quarter-century earlier. The number of C grades declined over the same period from 15 percent to 7 percent.

Under the new policy approved by the Princeton faculty, the university will strive to impose a 35 percent cap on the number of A's awarded. The quotas will apply to university departments rather than to individual professors, meaning that professors will continue to have some leeway in rewarding outstanding work.

Student reaction to the proposal has been "mixed," said Matthew Margolin, president of the Princeton student body. He said many students are worried that it will become harder to earn top grades from Princeton than from other comparable colleges, putting Princeton graduates at a disadvantage in applying for jobs and postgraduate work.

"Most of us feel that Princeton already has tougher grading practices than some of our peer institutions, so why do they need to tighten the standards even more?" he asked, citing the case of a friend who needed a 3.5 grade average to do postgraduate work at Oxford.

The rationing of A's could create an environment in which "everyone in the class is in direct competition with one another," said Erica Slep, a Princeton senior. "It will have a negative impact on the way students interact with one another."

Experts on grade inflation trace the phenomenon to the Vietnam era, when professors were reluctant to give grades that would lead to their students flunking out and becoming eligible for the draft. Grade averages tapered off during the '70s and '80s and then shot up again during the '90s, according to Stuart Rojstaczer, a Duke University professor who has collected nationwide data on grade inflation.

"The mid-'90s was when colleges started to treat students as consumers who are paying a huge amount for their college education, and should therefore get a good degree," Rojstaczer said. "The student is the customer, and the customer is always right."

Rojstaczer said that "a handful of selective institutions," including Princeton and Harvard, are trying to deal with grade inflation, but that others, such as Duke and Yale, "deny that the problem exists." A Yale spokeswoman confirmed that the university does not release data on its grading practices, on the grounds of academic confidentiality.

In the absence of a university-wide policy on grade deflation, individual professors say it is difficult to buck the nationwide trend toward awarding more A's. If a professor gains a reputation for handing out fewer A's than his peers, student enrollment in the lower-graded classes is likely to decline.

To get around this problem, Harvard professor Mansfield experimented for a time with a "two-track" grading system. He awarded his students an "inflated" grade that he reported to the university registrar and a "real" grade that he shared only with his students. He abandoned the practice last year after the university decided to slash the number of students graduating with honors from 91 percent of the senior class to about 50 percent.