The great state of Texas is famous for its cowboys, its Southern hospitality, its oil - and, within the United States, for the power it wields over the country's school textbooks.
Because of its size, Texas is the country's second-largest purchaser of textbooks - meaning that publishers, ever in pursuit of the largest possible markets, are under pressure to ensure they win approval from Texas State Board of Education (SBOE).
But this body has long been criticised as partisan, with SBOE members accused of trying to stamp their political and religious views on the school curriculum.
Dan Quinn, communications director at the Texas Freedom Network, an advocacy group that supports religious freedom, told Al Jazeera that the SBOE was bringing a far-right bias to Texas classrooms. "Social conservatives began a concerted effort to take control of the state board of education in the early 1990s," he said. "As that faction's power on the board has increased, so has its influence over the process of adopting state curriculum standards and textbooks that must be based on those standards."
He added: "The board's far-right bloc rejects separation of church and state, opposes teaching students responsible sex education, demands that biology textbooks include creationist arguments against evolution, dismisses concerns about climate change and other environmental problems, and promotes fear and ignorance regarding religious minorities in this country."
Evolution vs creationism
The teaching of evolution is perhaps the biggest lightning rod for debate. A recent discussion over which books should be used resulted in a delay in the approval of certain biology textbooks because of one board member's concerns with their treatment of evolution.
I am a creationist myself because I have looked at the evidence for evolution and found it weak. What I really want in schools is for the theory of evolution to be taught, not sold, to our children so they can draw their own conclusions.
"I don't think anyone should be required to leave their religious beliefs at the door," said Quinn. "On the other hand, public schools shouldn't be put in the position of having to choose whose religious beliefs to teach in their science classrooms."
But Don McLeroy, a former chair of the SBOE, told Al Jazeera that, while Christianity has influenced his selection of textbooks, he saw that as a positive thing. "I have never advocated creationism to be taught in schools," he said. "I am a creationist myself because I have looked at the evidence for evolution and found it weak. What I really want in schools is for the theory of evolution to be taught, not sold, to our children so they can draw their own conclusions."
While on the Texas school board, McLeroy backed a successful effort to add two standards to Texas' science curriculum, which required students be taught about the difficulties the theory of evolution has in explaining cell complexity and the appearance of stasis in the fossil record.
"The American Association for the Advancement of Science said the standards were 'a major blow to the teaching of evolution'. Three years later, a report by the Fordham Institute called our coverage of evolution in high school 'exemplary'. I say they are both correct."
The Fordham Institute, a conservative-leaning think-tank that monitors education in the US, claims that Texas takes an "erratic" approach to teaching evolution before high school, but its high school standards "handle the subject straightforwardly".
Writing the history books
Textbooks' coverage of US history is another breeding ground for controversy. The Fordham Institute released a report in 2011 calling Texas' history curriculum "unwieldy and troubling, avoiding clear historical explanation while offering misrepresentations at every turn".
This year a new set of textbooks used for history and sociology in Texas will be evaluated by the school board for approval. The SBOE has again come under fire, with some members accused of politicising the selection process.
"We hope decisions about which textbooks to adopt will be based on what the scholarship says, not the political beliefs of SBOE members," said Quinn. "But we're not naive. People want to see their cultural and personal beliefs validated, and they're uncomfortable and even angry when they perceive that as not happening."
The issue of separation of church and state has divided board members. "It's wrong to teach students that the nation's founders intended government to promote religion generally and, specifically, one religion over all others," said Quinn. "That's simply not true - but that's what some SBOE members want textbooks to do."
McLeroy countered that it was important for children to learn about the religious foundations of the US. "There is a liberal movement in the US that wants all mention of religion taken out of the history of our country," he said. "Our country had a religious foundation, and was founded for religious freedom - and we want to make sure that our children are taught that. What scares me is the rise of what I would call a secular religion in the country that wants to stop children from learning about the religious heritage of America."
Texas policymakers' national influence is not as strong as it once was, due in part to new technology and many states' adoption of "Common Core" standards for their curricula, creating a combined market bigger than that of Texas.
Kyle Ward, director of social studies education at Minnesota's St Cloud State University, explained that greater access to resources such as e-books has caused Texas' textbook influence to wane. But, he added, the state's sway persists. "It is my understanding that publishers have not gone through and made substantial changes to the texts," he said.
Ward, however, believes that textbooks are less important to educational outcomes than teachers' lessons and student research. "I always make the joke that I am probably one of the only people who has read a history textbook," he said, adding that with all the other resources now available, teachers rarely need to rely on textbooks in classrooms if they know the material well. "There used to be a belief that if a teacher said one thing and the textbook said another, the teacher was wrong. But now students can go and do their own research online."
Yet even if the Texas debate is losing some of its national significance, it still affects the millions of schoolchildren who live there - and, some argue, is tarnishing the state's reputation.
"These debates are bad for Texas," argued Quinn. "Businesses and researchers won't want to locate in a state that has a reputation as an educational backwater, so it's important that we end the culture war over textbooks and other instructional content."
Follow Philippa H Stewart on Twitter: @Flip_Stewart