Well, the US did abandon the gold standard, so I don't see any reason why that fact shouldn't be taught. It would only be a problem if the teacher (or textbook) took a position that this was a good or bad thing, without showing that there are (or were at the time) plausible arguments on both sides.

There's nothing like a little controversy to wake up bored students.

Here's an idea: assign two students to debate whether going off the gold standard would be a good thing. Have them debate it as if it hadn't happened yet, and have them use the same arguments that people used when the problem was being considered. Grade them not on whether their arguments are right or wrong, but whether they are historically accurate--do they accurately depict what some people once believed?

You could do the same thing with any issue that has been debated in the past.