The California Board of Education's recent decision to tell the nation's textbook industry to put more emphasis on evolution theory and human reproduction bucks a national trend toward more textbook censorship of sensitive subjects.

The unanimous vote by the board Friday to reject a whole genre of seventh- and eighth-grade science textbooks was unprecedented, according to state education and textbook industry officials. It was a direct challenge to Christian fundamentalists, who have consistently favored a superficial treatment, at most, of evolution theory and human sexuality.

The vote is expected to have far-reaching effects, since California represents about 11 percent of the nation's textbook market and publishers generally try to tailor textbook content to the wishes of the largest buyers.

"We must send a message to the publishing industry that we cannot tiptoe around certain subjects just because they are controversial," said Bill Honig, California's elected school superintendent. "Doing so undermines our efforts toward excellence in our classrooms."

In a telephone interview, Honig said he was aware that California's action counters the national trend toward textbook censorship by publishers and local school officials. A recent survey by the liberal group People for the American Way reported that incidents of censorship had increased 38 percent last year, with publishers routinely excising sensitive lines from such classics as Romeo and Juliet.

"Censorship is on the rise if nobody takes a strong stand for quality," Honig said. "Those people who stand up for quality are the antidote for censorship."

Textbook publishers have until Oct. 15 to tell California whether they intend to comply with the board's votes and rewrite their books by February. Most textbook publishers have indicated that they will comply, although they may not go as far as the state would like.

"To put human reproduction in a junior high school math book could conceivably hurt us in other markets," said Roger Rogalin, editor in chief of the D.C. Heath Co. publishers in Massachusetts. "We're not going to give up 90 percent of the market to get 10 percent."

He added that his company will analyze California's request before deciding what to do. The request for more material about human reproduction might be met by using supplements, without changing the text of books, he said.

The board members said they rejected the science textbooks because the publishers had "watered down" discussion of evolution and human reproduction, in deference to the New Right. Some Christian fundamentalists have argued that creationism -- the belief that the world was literally created in seven days -- should be taught in classes alongside of evolution theory.

Since 1975, California has not allowed the teaching of creationism in science classes. Creationism may be taught only in history or other social science classes.

California school officials said the board's vote Friday was not an issue of evolution versus creationism but a matter of improving the way in which evolution is taught.

"We want accurate, up-to-date explanations," said Francie Alexander, director of the state's Office of Curriculum Framework and Textbook Development. "We see no conflict with religion. It is not a hostile position to religion."