The Lone Star State is famous for one great horror movie, “The Texas Chainsaw Massacre.” Here’s another, but it’s a documentary—Scott Thurman’s “The Revisionaries.” It isn’t a horror movie in the conventional sense, of course. There are no slashing knives and falling bodies. But there are plenty of scissors snipping facts from school textbooks for ideological reasons, and intellectual integrity and scientific rigor suffer hit after hit. And that, in its own way, is as frightening as any tale of deranged families waylaying unsuspecting passersby with implements of torture.

The film’s focus is on the Texas State Board of Education, an elective body that enjoys unseemly power over the content of textbooks used nationwide—and, under the dominance of right-wing members, has exercised it to manipulate the state’s “standards” to conform to their ultra-conservative views. As the filmmakers note, the effort is especially intense in the sciences, particularly in an attempt to denigrate Darwinism and the theory of evolution in favor of an approach that will introduce creationism into the required curriculum, often in a veiled and surreptitious fashion as “intelligent design.” Fundamentalist activists like board member Cynthia Dunbar, who proudly brandishes degrees from universities founded by Pat Robertson and Jerry Falwell, appeal to the principle that all “points of views” should be discussed by students as the rationale behind their advocacy. But the many scientific experts who appear before the board bring the matter back to rationality by noting that opinions with no evidence behind them do not deserve an equal footing in science classrooms as theories that do.

That idea finds no support from the man who becomes the main actor in the real-life drama—Don McLeroy, a small-town dentist who talks about “standing up to the experts” in support of his literal reading of the Bible. He readily admits believing that the earth was created six thousand years ago and that Adam and Eve walked with dinosaurs, and expresses his opinion to captive patients. Despite an almost irresistible invitation to do so, the film doesn’t stoop to ridiculing McLeroy; as a matter of fact, he emerges as a rather likable, if pathetically misguided, figure, convicted not so much by opponents like Kathy Miller of the Texas Freedom Network and soft-spoken Professor Ron Wetherington of Southern Methodist University as by his own words and the illogic of his arguments. Indeed, the film concludes with his reelection campaign against a relatively moderate Republican, which doesn’t result in his vindication, and one leaves feeling rather sorry for him.

But he and his like-minded colleagues have already done their work, which won’t be reassessed for another decade. And it’s not merely the science textbooks that suffer the slings and arrows of the board. McLeroy, Dunbar and their allies also take off after the social science—or more properly history—books, suggesting that they summarily jettison mention of such suspect figures as Thomas Jefferson and replace them with more acceptable subjects like Phyllis Schlafly. And they enjoy a good deal of success, partially due to the willingness of more liberal board members to compromise.

The educational ramifications of all this are horrible enough, but the really terrifying idea at work here is the very idea that such matters should be decided by people with ideological and religious axes to grind, chosen by an electorate motivated by the same assumptions. The result in Texas has been a disaster by any objective standard, and the whole country will unfortunately feel the effect.

“The Revisionaries” presents this unhappy reality with as little rancor and cinematic foot-stomping as possible—this is a deliberately understated piece, entirely conventional in its assemblage of interviews, footage of board meetings, and material filmed outside the boardroom (as in McLeroy’s dental office) and avoiding any hint of shrillness. But its point of view isn’t difficult to discern. By letting all the flowers in this debate bloom, as was once observed, it allows the poisonous ones to be clearly seen. This is at once an unsettling documentary and an enlightening one.