Scatalogical "Humor"

[Venus193]

Zip, the only attention I would have gotten for something like that would have been getting my face slapped.  I had classmates whose parents would wash their mouths out with soap.

[ZipTheWonder]

The fact that attention-seeking is developmentally normal  for children doesn't mean they know how/when to do it appropriately.  It just means that, as a species, it's vital for us to learn to raise attention.

[Lisbeth]

I have an old friend of 26 years' standing who permits her third-grade son to tell fart jokes.  I realize that potty mouth is common among kids at toilet-training stage, but he is way beyond that.  Someone even gave this kid a "disgusting jokes" book for Christmas.

Is there any polite way to tell her and her husband that this kind of talk will be counted against their child by others?

None that I can think of that wouldn't be an etiquette violation in itself or wouldn't be seen as "telling them how to raise their child."  Nothing raises parents' hackles more.

I think your best course of action is simply to ignore it while it's happening in front of you.  If the kid tries to tell those "jokes" to you, I'd say, "Uh huh" in monotone and with a blank facial expression and change the subject.