A Prince George's County teachers union said yesterday that teachers give Superintendent John A. Murphy a "C-minus" rating and believe publicity about his achievements has been overblown.

The union's May survey of about half of the county's 6,700 public school teachers was immediately denounced by school officials as a ploy in the union's effort to retain the right to represent teachers.

Teachers are scheduled to vote Friday on whether the Prince George's County Educators' Association will continue to represent them, or if they will join with members of the Prince George's County Federation of Teachers. The federation has begun a fierce, well-financed campaign that charges the current union leadership has a contentious relationship with school officials.

The survey, developed and analyzed by the educators association and its state and national affiliates, rated Murphy as average overall and gave him a C-plus rating for leadership. The survey said low teacher morale, increasing demands on teachers and overemphasis on standardized testing were cited as major concerns. Nonetheless, 75 percent of the teachers responding to the survey said they wanted Murphy to remain as superintendent.

At a news conference announcing the survey results, Dale A. Robinson of the National Education Association, the union's national organization, repeatedly said the survey was "not an attempt to go after" Murphy but to highlight teachers' concerns.

"We're not here to bash the superintendent but there are some areas where we would like to see some B's and A's," Robinson said. He added the board should include such school-based assessments in the formal evaluation process conducted by the Board of Education.

Murphy declined to comment yesterday on the survey, but school spokeswoman Bonnie Jenkins said, "It's very difficult for us to take this seriously. We see it as a political ploy as they are desperately trying to hold onto their membership."

The superintendent was assigned one of his lowest ratings on a question about how he accepts criticism. In evaluating the superintendent's impact on achievment at individual schools, 80 percent of the respondents said they felt pressure to inflate grades they give students.

The county Board of Education announced in April that Murphy would receive a $45,000 raise and a 10-year contract, an effort to keep him from seeking work elsewhere. That action caused an uproar, as some citizens criticized the superintendent for placing too much emphasis on test scores and doing too little to improve black achievement. Murphy withdrew from the controversy and turned down the raise.

Board of Education member Marcy Canavan, who is overseeing the board's evaluation of Murphy, criticized the survey for what she called slanted questions and the union for misleading teachers into thinking it would have some bearing on the board's actions.

Educators association leaders said the impending summer school break made it necessary to release the survey this week. "We decided it's important for the Board of Education to hear teachers," Robinson said.

While Murphy's formal evaluation by the board is a private personnel matter, the board will announce at its June 28 meeting whether he will get a raise.

Rosalind Johnson, president of the federation, which is challenging the educators association, said the survey is inappropriate at a time when teachers and school officials are involved in critical negotiations about health care. "I cannot understand why a teachers union . . . would continue this antagonistic, negative kind of propaganda," she said.