What is the Source for David Barton's Kids with Guns Story? (UPDATED)

UPDATE (2/26/13) – David Barton responded to this post on his website, admitting that the kids with guns story came from a Louis L’Amour novel.  He claims that sharing this story as historical fact is alright since L’Amour claimed the story was true. I examine that claim and compare it to the story of George Washington and the cherry tree in this post: David Barton, Kids, Guns and Historical Fiction.
(Original post begins here)
On January 16, on the Glenn Beck Show, David Barton claimed that the National Rifle Association was started in part to arm newly freed slaves against the KKK and that Ronald Reagan opposed the Brady Bill. However, these claims are false.
In that broadcast, Barton also related a story about a school in the 1850s where school children stopped the murder of their teacher by pulling their guns on a would-be assailant. The story sounded fishy at the time but he did not give any details which would allow the facts to be checked out.
Now Chris Rodda is wondering if the story may have been lifted from a Louis L’Amour novel. After reading her post on the matter, I wonder the same thing.  Go read it and see what you think. Here is what Barton said on Beck’s show:

The great example, in the 1850s you have a school teacher who’s teaching. A guy — he’s out in the West — this guy from New England wants to kill him and find him. So he comes into the school with his gun to shoot the teacher, he decides not to shoot the teacher because all the kids pull their guns out and point it at him and say, ‘You kill the teacher, you die.’ He says, ‘Okay.’ The teacher lives. Real simple stuff. Saved the life of — there was no shooting because all the kids — we’re talking in elementary school — all the kids pull their guns out and says, ‘We like our teacher. You shoot our teacher, we’ll kill you.

One of Rodda’s readers thought the story might have come from a Louis L’Amour Western novel (as did this Crooks and Liars commenter). Go read the account from the novel in Rodda’s post but the punch line is that it sounds remarkably like the L’Amour fiction. In response, Rodda issued a challenge for Barton to produce the historical source for his claim.  With this post, I join in asking for the source.
While the story is somewhat far fetched and perhaps even a little humorous, the challenge raised by Rodda is a serious matter. Mr. Barton’s and his defenders now have a perfect opportunity to verify this claim and to address his wounded credibility. Will he do it?
UPDATE: Here is the entire chapter in the L’Amour book where the school teacher is saved by his gun-totin’ students. Here is another chapter which describes the kids bringing guns to school.