Texas this week joined two other educational reform-minded southern states in requiring that their 210,000 public school teachers take a competency test in reading and writing. Most of those teachers said the exam was embarrassing and unnecessary. Are they right?

Last summer, when Arkansas became the first state to give a competency test for reading, writing and math skills to veteran teachers, the reaction of those teachers was pretty much the same. The test seemed ludicrously easy. That was exactly the way most teachers were supposed to find it, with multiple choice math questions as simple as: "A student answered 96 out of 120 questions correctly on a final exam in chemistry. What percentage of the test items were answered correctly by the student?" The writing test? In 250 words, write a recommendation, or write about a discipline problem, or write about a project. The problem that made that simple test necessary was the fact that 10 percent of the teachers in Arkansas flunked it.

The Texas test is said to be high school level. After taking it, one instructor said: "If you flunk that test, you shouldn't be teaching." Not one of the teachers opposing the exam would want his or her children in a class with an instructor who flunked it. School systems need tests to identify any such teachers and remove them from the classroom; or they need rigorous evaluations that do the same.

Yet there seems to be an idea floating around that teachers are above this sort of scrutiny, that we insult a vast majority of competent teachers when we ask each of them to take such a test. The D.C. school board, for example, did not want to risk the ire of the Washington Teachers Union by implementing a test for veteran teachers.

But the only valid criticism of the Arkansas example is that the process is too lenient. The Arkansas teachers who failed the test can take it as many as five times until June 1987; and they can take remedial programs to help them prepare for it. Even after repeatedly failing, they could not be fired in June 1987. State law says that they can continue to teach until their certification expires, even if that is years down the road.

In Texas, where 95 percent of the teachers are expected to have no trouble passing the test, State Education Commissioner W. N. Kirby said those teachers who fail get only one more chance to pass. If they flunk it then, they are supposed to be fired. "We believe children have rights too," Mr. Kirby said, "a right to have teachers with the necessary basic skills in the classrooms." That is the proper goal. The worst mistake would be to fail the children by not dismissing failed teachers.