Truth in Texas Textbooks formed last year to shape how climate change and scores of other topics are taught. It has no political or religious affiliation but organizers recruit volunteers through tea-party networks and church groups—as well as teachers associations, Rotary clubs, and other civic organizations—and have accused publishers of creating textbooks with an "anti-Christian" and "anti-American" bias.

Teaching that the global-warming theory is controversial reflects public opinion, as there is a sharp divide over the connection between human activity and Earth's evolving climate. But that approach is sharply at odds with climate scientists, who nearly universally believe the former is driving the latter.

Textbooks are often the first conduit between climate science and young people. The books that the Texas truth coalition is fighting over are expected to be used by more than 5 million Texas public school students for at least a decade. Texas is also the second-largest market for textbooks behind California, and publishers often peddle best-selling Texas textbooks in other states.

And that's not all: The coalition's system of rating textbooks could soon spread beyond Texas. White says that activists in California, Florida, Indiana, Maine, Nevada, Ohio, Utah, and Wisconsin have already contacted the coalition to learn how they can create their own rating system.

Advocacy groups giving grades to Texas textbooks is not novel: A conservative Christian organization called Educational Research Analysts has been rating educational material in the state since the 1960s. The group questions scientific evidence for evolution and supports education that promotes abstinence until marriage. Educational Research Analysts also has ties to the Texas truth coalition: Its president, Neal Frey, advised White as he worked to get Truth in Texas Textbooks off the ground.

But Educational Research Analysts hasn't worked on climate science, which is a targeted area for Truth in Texas Textbooks.

So far, however, the group has struggled. The coalition faced a setback when the Texas Board of Education voted last month to adopt new social-studies textbooks for public schools. Ahead of the vote, major publishers—including McGraw-Hill and Pearson—stripped out passages that cast doubt on climate change. The revisions followed fierce criticism of the content from groups like the Texas Freedom Network, a left-leaning advocacy group that pushes for man-made global warming to be taught in the books, and Climate Parents, an organization dedicated to teaching climate science.

Eighty-nine new social-studies textbooks have now been approved in the state. But school districts have a lot of leeway over exactly which books to buy, a series of decisions that they're slated to make this spring.