The Supreme Court's recent ruling that Louisiana's "equal treatment for creation science" law is unconstitutional is no guarantee that the pseudoscience of creationism will be kept out of our public schools.

In his majority opinion, Justice William Brennan made it clear that the law was struck down because its primary purpose was to advance a particular religious belief. Nowhere in the decision, however, did Brennan ever say it was illegal to teach creationism in the public schools.

Creationists, seeing this as an opening, have vowed to renew the battle at the level of the local school board. Organizations such as the Institute for Creation Research have declared that they will now work harder than ever to persuade teachers either to omit evolution entirely or to teach creationism along with it.

Unfortunately for our children, the creationists are likely to be successful unless we are careful. This, at least, is the conclusion I draw from a study I have recently completed of the opinions of high school biology teachers in Ohio. Almost 40 percent of teachers polled for this study favor teaching creationism in public schools. Even worse, at least 15 percent of the high school biology courses in Ohio in 1986 were presenting creationism in a favorable light.

True, evolutionary biology is being presented in 88 percent of the high school biology courses in Ohio. But remarkably enough, this figure is seven percentage points lower than was reported in a nationwide study in 1942.

My study also asked teachers whether they had experienced any pressure to alter the course content of their science classes. Pressure was reported to have come from a variety of sources: religious figures, school administrators, parents and even God. I found that creationists were applying significantly more pressure than were proponents of evolutionary theory.

Evolutionary theory is central to biology and completely incompatible with the doctrinaire views of creationism. Regardless of how much noise the creationists make, the issue is one neither of freedom of speech nor of a close-minded scientific community's refusing to air alternative views.

Creationism is a pseudoscience because it professes to know all of the answers. It is untestable and immutable. As Henry Morris, director of the Institute for Creation Research, has written, "If man wishes to know anything about creation, his sole source of true information is that of divine revelation. God was there when it happened. We were not there. Therefore, we are completely limited to what God has seen fit to tell us, and this information is His written Word. This {the Bible} is our textbook on the science of Creation."

Why are so many high school biology teachers in favor of teaching the pseudoscience of creationism? The most striking explanation in many cases may be that the teachers themselves are poorly educated about evolutionary biology. For example, when asked to choose the sentence best describing evolutionary theory from five choices offered, almost one-quarter indicated that evolution involved some sort of purposeful striving toward "higher life forms."

Such a view, by postulating an externally directed purpose and direction to evolution, is antithetical to its main principles and is also beyond the realm of science. Only 11 percent selected the correct choice: that evolution occurs because individuals produce different numbers of offspring. Furthermore, only three-quarters of the teachers indicated that evolution has a valid scientific foundation. Imagine the uproar that would ensueif such erroneous views were presentedto public school students in any othersubject.

What can one survey from Ohio tell us? Just this: that even in a northern industrial state that has experienced little pressure from creationists in recent years, creationist viewpoints are finding their way into public school classrooms. It tells us that the level of scientific sophistication, even among high school biology teachers, leaves much to be desired. Many of our teachers cannot successfully educate our children when they themselves display such ignorance of fundamental biological principles.

Most significant, however, the Ohio survey should warn us. As the creationists move to the local level in response to the Supreme Court ruling, they may very well find many allies.

The biological and political decisions our society has to face in coming years are awesome. If we are to make informed decisions about such biological issues as AIDS prevention, genetic engineering, advances in reproductive technology and cancer treatments, to name just a few, we must understand basic biological principles. We owe it to our children and to our society to have our schools offer the best information that we have, not the outdated, unscientific ideas of centuries past.

The writer is a professor of biology at Oberlin College.