William Bennett, the chairman of the National Endowment for the Humanities, yesterday said the agency has been hit by "grade inflation."

"I read a proposal through and say, 'Well, it's okay,' " said Bennett. "Then I read the panel review of it and it says 'A.' I read it and say 'B minus.' "

At a 45-minute meeting yesterday, Bennett told NEH staff that the agency should raise its standards as its budget tightens.

"The budget is down," he said, "and the burden of proof on the applicant is higher." Bennett said he asked the staff to "really press the panels and reviewers for really candid evaluations of applications ."

Asked if he would approve the 'B minus' applications, he said, "I don't know. I'll read them again."

Bennett met with reporters after the meeting. Since he became chairman two months ago, President Reagan has marked the NEH's fiscal 1982 budget of $130 million for a cut to $96 million for fiscal 1983.

Bennett did not specify the areas in which standards could be raised. "It's not endemic to any one of the departments," he said. "It's across the board."

Bennett told the National Council on the Humanities almost two weeks ago that he reluctantly approved several grants because those applicants had already been told to expect funding. He also noted yesterday that he would not be shy about disagreeing with the council on a grant application it had recommended. "I have to have the last word ," he said. "They're advising. I established at the last meeting that we will disagree--hopefully without rancor."

In addition to the rise in standards, Bennett told reporters the agency would start a seminar program for secondary school teachers, initiate a "chairman's awards for excellence" program for state humanities councils, invite applications for "appropriate celebration" of the Bicentennial of the Constitution in 1987, and consider a recognition award for people doing outstanding work in the humanities.

The seminars, slated for 1983, will offer secondary school teachers "an opportunity to be scholars and students once again," said Bennett. "The endowment should not be concerned only with colleges." There will be 10 to 15 seminars initially, with 15 to 20 teachers per seminar. Bennett estimates the cost of 15 seminars at $750,000.

The chairman's awards for excellence in the humanities would be $75,000 grants given to 10 state humanities councils. By congressional mandate, NEH puts aside 20 percent of its total budget for the states, some of which is allotted to each state by formula. Bennett plans to use the leftover amount, slated for discretionary use by the chairman, for the awards.

The recognition award Bennett discussed would "honor, award, thank individuals or agencies . . . for serving any of the same mandates of this agency, whether or not they have gotten money from us," he said. It would honor "that librarian who is getting books to kids, that outstanding teacher, an excellent museum administrator."