When Frank Shaffer-Corona shows up at forums for D.C. school board candidates, the challengers who want to take away his $18,000-a-year job act as though they see a big red bull's-eye painted on his back.

Shaffer-Corona is Target A of this year's campaign for at-large seats on the board. A key contention of most challengers is that it is time to bring some dignity to the board, to cut out the antics. And they say that no one has an image that better personifies those antics than Shaffer-Corona.

The 38-year-old Shaffer-Corona made $1,900 worth of telephone calls to Tehran, at school board expense, in a personal attempt to negotiate the Iranian hostage crisis. He went to Beirut in his effort at personal diplomacy, and says he met with representatives of the Palestine Liberation Organization. He used school board funds to attend a youth conference in Havana. He has been arrested for allegedly interfering with a police officer trying to make an arrest. He is the only member ever censured by the board.

The challengers usually don't even mention his name. They just tell an audience that it's time to remove "international politics" from the board's agenda, as one candidate did recently, and everyone is supposed to know who they're talking about. Sometimes the remark has drawn laughs, other times it has fallen flat.

But the same Shaffer-Corona who finds himself in the middle of the free-fire zone is also the city's highest-ranking Hispanic official and not all Hispanic activists disown him.

He has argued in support of bilingual education, an important issue for Hispanics. He is well-known in his stomping ground of Adams-Morgan, where his more controversial exploits have been noted, but perhaps not so roundly denounced as on editorial pages and in television commentaries. And on the campaign trail, he can be easy-going, self-effacing, even possessed of a certain amount of charm.

"When I was elected I promised to work for you and raise hell," Shaffer-Corona told one campaign gathering. "Well, you know I've raised a lot of hell."

Shaffer-Corona, who once supported himself as a backgammon player at an Adams-Morgan bar, seems to relish the controversy. "If I was the dumb little Mexican and took whatever they gave me, they'd love me. They'd love me!" he says of his detractors. Then he breaks into an exaggerated Mexican accent, imitating the Shaffer-Corona he says his enemies would love to hear: "Could we pleeze, senor, have whatever scraps you would like to geeve us? Pleeze?"

When Shaffer-Corona won his school board seat four years ago, the other candidates for the two at-large seats then up for grabs were incumbent Barbara Lett Simmons and representatives of two fringe parties, the Socialist Workers Party and the U.S. Labor Party. Simmons led the field with nearly 22,000 votes, and Shaffer-Corona beat out U.S. Labor Party member Stuart Rosenblatt for the second seat, 11,640 to 9,252.

This time around, though, there are 17 contenders for the two seats, including such challengers as the Rev. David Eaton, Phyllis Young, Frank P. Bolden, Manuel Lopez and Jonas Milton, candidates with solid backgrounds who have received numerous endorsements.

Sharon Pratt Dixon, D.C. Democratic national committeewoman, says of Shaffer-Corona, "It's difficult to find Frank's friends in the Democratic Party." One party official put the assessment in harsher terms, calling Shaffer-Corona "a hopeless flake."

In 1977, Shaffer-Corona portrayed himself as a spokesman for the Hispanic community, through his status as Washington representative for La Raza, a nationwide organization. But many Hispanic leaders began criticizing him almost immediately after he took office. His support among Hispanics this year is questionable, although Hispanics have not constituted a large voting bloc in the city.

Harry Quintana, a former Advisory Neighborhood Commission member in Adams-Morgan, has what may be the majority view: "There is not a reasonable, intelligent Hispanic leader who has said that Frank has done anything for the Hispanic community. His rhetoric is all leftist and makes no sense at all. I cannot make sense in any way or another of what he stands for."

But Willie Vazquez, who heads the city's Office of Latino Affairs, offers a different view: "Quiet as it's kept, he ain't all bad. We have to take Mr. Shaffer-Corona seriously. The fact is that he has steadfastly raised some issues with regard to Hispanics." Vazquez mentioned Shaffer-Corona's longtime support of bilingual education programs as an example of his contribution to the school board.

The walls of Shaffer-Corona's office are papered with posters of revolutionary figures like Che Guevara and Yasser Arafat. During an interview on a recent morning, he wore a yellow T- shirt, proclaiming "Love is . . . loving a black child."

Prior to the interview, Shaffer-Corona provided an inch-thick sheaf of documents making his case to refute those who do not take him seriously. The documents included a speech he gave to a youth conference in Havana in 1978, as well as a study on teacher salaries he did in 1979 to help persuade the board to finally settle the teachers' strike of that year, and a recent study of school closings.

He said he believes school closings will be the major issue confronting the board after Tuesday's election and warns against closing schools that could be needed in the future if the District's population starts increasing again.

He is serious about his work, he says; the negative image "has been created by The Washington Post." Shaffer-Corona attacks The Post at campaign appearances, at times with success. At a recent forum in far Southeast, when he said that The Post is "dedicated to the defeat of minorities," the mostly black audience applauded.

Shaffer-Corona has given several justifications for his attempt at global diplomacy during the hostage crisis. He said recently, "I'm not just an educational technician. I am a keeper of the public trust . . . D.C. doesn't have senators or congressmen to do this kind of thing for them."

He says he has learned two things from the experience: "First, that this country has got to start learning to get along with people. Second, that anybody with a little creativity, imagination and education can go out and be their own State Department."

As he launches into a discussion of world affairs, Shaffer-Corona is asked whether a school board member's attention is properly focused so far from home, and he has an answer.

"When I concentrate on these more parochial matters . . . they get even more upset." And he laughs.