Montgomery County school officials began an investigation of a part-time teacher yesterday after parents complained that their children said the instructor called the Rev. Martin Luther King Jr. a "communist."

Connie Bishop, an advocate with the NAACP, said a parent of a sixth-grade student at Bel Pre Elementary in Silver Spring wrote a letter to Principal Aileen Craig expressing concern about comments allegedly made by Karen Collins, a part-time music teacher. Collins, who is white, allegedly made the remarks about King last Thursday to a black teacher during her preparations for King's birthday observance.

The letter, which was read to a reporter by NAACP President Roscoe Nix, said, "It is our strong opinion that a teacher that harbors such a clearly prejudicial opinion and freely expresses it in connection with the performance of her public responsibility is unfit to teach in any public school system." Nix and Bishop declined to name the parent who signed the letter.

School spokesmen said yesterday afternoon that the letter triggered their investigation.

Bishop said she and Nix received complaints from the parents late last week prompting the organization to investigate the incident.

School spokesman Bill Henry was quoted yesterday by wire services as saying Collins did not call King a "communist," but that she said she was reluctant to prepare music for a school program she was asked to organize, because "she read King had communist friends and supported communism."

Later yesterday, however, Henry declined to comment until the investigation is finished. School officials said Collins declined public comment.

Another school spokesman, Sally Keeler said, "It would be inappropriate for us to speculate on what may or may not have been said. This personnel investigation is our standard policy, so we can ascertain what happened and make a recommendation."

Keeler said Collins entered another teacher's classroom at the school, which has a 26 percent black enrollment, to discuss the program preparations with that teacher and was overheard by students to have said "something about Dr. King and communism and the parents heard about it."

"We are awaiting the school's response and our own investigation," Nix said. "But, if we find the allegations are true, after talking with the parents we (the NAACP) will ask for her removal . . . . Any person who says Dr. King was a communist is either maliciously racist or uninformed."