Country music is an important modern cultural movement; hip-hop isn't. Thomas Jefferson deserves to be erased from a list of "great Americans", but Ronald Reagan doesn't. And we should re-evaluate Senator Joe McCarthy: he was almost certainly a national hero.

If you think that sounds like a quirky rewriting of American history with a right-wing twist, then you're not alone. But if the state of Texas gets its way, it'll be what teachers across the rest of the nation are required to tell their students.

In a move that has sparked controversy from coast to coast, together with a slew of headlines about the "Texas schoolbook massacre", the Lone Star state has just narrowly approved a series of conservative-minded alterations to its social studies curriculum.

The school board's decrees range from the surreal to the faintly sinister. One dictates that the Republican former House speaker Newt Gingrich should be studied. Another says that the speeches of Jefferson Davis, the slave-owning president of the Confederacy, should be taught alongside those of Abraham Lincoln. And the National Rifle Association should be praised for upholding the Constitution.

These and many other changes were approved by the board earlier this month, following three days of rancorous debate in Austin, the state capital. The vote of 15-5 in favour of the move was made entirely along party lines: every Republican on the committee approved them.

To the rest of America, the board's colourful right-wingery ought to be nothing more than a colourful sideshow. But the economics of the education industry mean otherwise: Texas is the biggest market for new teaching materials in the country, with 4.7 million schoolchildren, meaning that its curriculum influences the contents of textbooks nationwide.

Historians this week voiced concerns about the proposed revisions, many of which they have described as inaccurate. They are particularly angry that Jefferson's importance to the nation's founding fathers will in future be played down. That change to the curriculum was supported by evangelical Christians, who dislike Jefferson's support for the separation of church and state.

"The books that are altered to fit the [new] standards become the bestselling books, and therefore within the next two years they'll end up in other classrooms," Fritz Fischer, chairman of the National Council for History Education and a vociferous opponent of the changes, told The Washington Post. "It's not a partisan issue; it's a good history issue."

Elsewhere, the new curriculum allows teachers to treat country and western music as a significant cultural movement. But a move to add hip-hop to the same list was voted down by conservatives.

Students of Cold War history looking at McCarthyism must in future be told that the Verona papers, which documented communications between the Soviet Union and its spies, "confirmed suspicions of Communist infiltration in US government". In fact, historians are divided on whether this is really the case.

Controversy over the changes has shone a spotlight on the powers and make-up of the 15-strong Texas board. One of them, a dentist called Roy McElroy, failed by a whisker last year to get the board to force the teaching of Creationism alongside evolution in science lessons. This year he supported a successful move to have the term "capitalism" replaced with "free market enterprise" in classes.

Texas has a long and storied tradition of political interference in the educational process. Since the 1970s, evangelicals have repeatedly tried to have books seen as anti-Christian removed from its syllabus. Conservatives have also attempted to prevent children being taught about gay rights and global warming.