Across the country, but especially in the South, competency tests to screen prospective teachers are eliminating blacks and other minorities from the profession at what some educators call alarming rates.

"We don't want anyone in the classroom who can't handle the very things they're trying to train children to do," said Ralph Turlington, Florida's commissioner of education. His state's test measures an applicant's ability to perform arithmetic at an 8th- or 9th-grade level, to read, write an essay and to utilize "professional skills."

"We have a test every teacher ought to be able to pass," he said.

But Walter Mercer, a professor at predominantly black Florida A&M University, said, "The test is killing future black teachers. It's an academic electric chair." Only 37 percent of Florida A&M students who took the state test passed it, a pass-rate similar to many other black colleges across the South.

By 1985 at least 25 states are expected to require some kind of teacher licensing exam similar to those now used in most southern states. In California, seven out of 10 minority teacher applicants flunked the state's first licensing test in December, among them a disproportionate number of blacks and Hispanics. In Arizona, three out of four blacks and American Indians who took that state teacher exam failed it last year. Two out of three Hispanics flunked, compared with a white failure rate of one in four.

In Alabama, Mississippi, Georgia and many other southern states the pattern was the same: most blacks, usually educated at predominantly black instititutions, are failing the tests.

So serious is the qualified teacher shortage in Louisiana that 834 teaching vacancies are filled with non-certified teachers. Black college test scores have edged up since the state began testing five years ago, but fewer blacks are taking the test, said Robert Crew, director of higher education and teacher certification.

"The number of people entering education has decreased among both white and black," he said. Starting teacher salaries, between $11,000 and $13,000, fall far below those of other fields.

Only one-third of Florida's black teacher applicants passed a recent licensing exam, compared with 90 percent for would-be white teachers. But the state-developed test was regarded as so elementary that the state board of education recently raised the minimum scores required to pass.

Turlington said a statewide poll showed that blacks, whites and Hispanics favored tightening standards. "The time is over when we're going to accept a diploma at face value," he said. "We don't do it for nurses, doctors, pharmacists or attorneys. Why should we do it for teachers?"

He added: "If we set professional standards, the challenge will increase the public esteem of teachers , and more will aspire."

Many critics say that the reason many blacks fare so poorly on the tests is that they are graduates of predominantly black colleges that have suffered from skimpy funding for generations. A 1975 class-action lawsuit in Mississippi charges that the state fueled the decline of black colleges through discriminatory funding. Three black graduates who failed the tests in Alabama last year charged in federal court that the exams tested information that had not been taught and the questions were racially biased.

Florida A&M worries that a new state law could strip its education program of accreditation if not enough students pass the state's basic skills test. Another Florida law requires students to pass a pre-screening test before they can enter college education programs. High school students must pass a basic skills test before they get their diplomas.

"The test results indicate that we need to do some things differently, but we are going to meet the challenge of the test," vowed Walter Smith, Florida A&M's president, who said he fears that there will be fewer black role models for black youths if the tests keep blacks out of teaching. But he conceded that "It's hard to place the blame."

Students such as Edna Johnson blame the tests.

At 45, Johnson enrolled at Florida A&M with the dream of becoming a teacher. She earned a B average, then flunked the state certification test after being graduated last year.

"We grow up thinking black, but the test is written for the white man," said Johnson. She is now teaching a special education class of third and fourth graders in Perry, Fla., under a provisional license that gives her three years to become certified.

She cited as an example of cultural bias one question that asked how to discipline a rowdy student properly. "The answer they wanted was to stand by his desk until you got his attention," she said. "But most blacks believe in spanking. You need different techniques for different children. You can't always go along with the white man's way of thinking."

Test-makers deny any built-in racial bias and say they are willing to throw out unfair questions. Thomas Fisher, who runs Florida's teacher testing, says math skills tested are 8th- or 9th-grade level. "A good high school student" should be able to pass the reading and writing portions, he adds.

"If they can't pass, they can't teach," said Eva Galambos, staff director for the Southern Regional Education Board task force on higher education. "If you saw the questions, you'd wonder, 'Aren't these the minimum standards we've got to insist on for the next generation of children?' " But test critics, including the 1.2 million-member National Education Association, which represents most of the nation's teachers, argue that such tests cannot predict what kind of teacher an applicant will make.

"A single test can't measure other factors that make a good teacher, like patience, understanding and empathy," said Ron Vera, attorney for the California-based Mexican American Legal Defense and Education Fund. "The tests cannot predict how well someone will teach," agreed William Harris, director of teacher programming for the Educational Testing Service. "They are knowledge-based tests that only give an indication of what a student knows after finishing a teacher-training program. They don't predict performance in class." A Georgia study found little relationship between teacher scores on certification exams that tested for content knowledge and a teacher's ability to "put it over" in class.

"I'm sympathetic to compensating blacks for the sins of our fathers," says Tom Bordeaux, a white lawyer on Mississippi's college board. "But it's not intellectually honest to set two standards, one for black teachers and another for whites. It will only perpetuate a system where black children will be victimized by a system that victimized their parents and they won't be able to cope in our highly technical and computerized society."

Some black educators insist that the tests are necessary to restore public confidence, even if it means keeping blacks out of teaching during a painful "shakeout period."

"I have a problem with testing--some people just go into a shell like an oyster when you say 'test'--but the overriding issue is competency in the teaching field," said George Watson, 57, a black public school assistant superintendent in Bay Saint Louis, Miss. "We have a responsibility to the child, and if we put an inferior teacher in the classroom we do that child an injustice. We are going to lose some blacks, but that's a price we have to pay.