A Harvard University study issued this week confirmed reports of grade inflation at the prestigious Ivy League school, revealing that about half of the grades issued last year were A's or A-minuses.

The report tracked grades given at Harvard for the past 15 years and documented a steep increase in top grades in the last decade. A's and A-minuses accounted for 33.2 percent of all grades in 1985 but a staggering 48.5 percent last year. Failing grades, D's and C's made up less than 6 percent of all those given.

"With such a narrow range of grades available, faculty find it difficult to distinguish adequately between work of differing quality; they may also be unable to make such distinctions clear to students," wrote Susan Pedersen, dean of undergraduate education.

The dean's office has no official power over the faculty. However, the dean can direct the departments to study the issue and push for change. It's the first time the university has indicated it will do something to remedy the situation.

The findings vindicated the three-decade crusade of one Harvard professor, Harvey C. Mansfield, who grabbed headlines earlier this year for his policy of issuing two grades to students -- the official, inflated one matching university standards and the one they deserved.

"I'm very glad the university is discussing the matter and is going to do something," Mansfield told Fox News in an interview. "It is a scandal -- and this is proof. It's bad for our reputation because we look so lax."

Some of the factors driving professors' generosity with grades were pressure to grade similarly to colleagues, fear of becoming known as a "tough grader," and pressure from students accustomed to higher grades, the Harvard study said.

The good grades may also be deserved, as students work harder and are better prepared, it said.

The highest rate of A's came out of small humanities classes, making up almost two-thirds of all grades given. Social science classes with 75 students or more were the toughest, with a third of all students receiving A's or A-minuses.

In October, The Boston Globe reported that nine in 10 Harvard students graduated with honors, which takes at least a B-minus average in the student's major.

By comparison, honors went to 51 percent of graduates at Yale and 44 percent at Princeton. Other Ivy League universities also had a much lower rate of honors students than Harvard.

Fox News' Catherine Donaldson-Evans and The Associated Press contributed to this report.