If a group of people believing a random untrue fact is a threat, there are a vast number of threats out there. Far more than the school system can possibly deal with. Misidentifying the age of the earth is harmless compared to things like economic misconceptions and there aren't many school systems making a credible effort to correct those.
I actually had a young earth creationist say that the sun doesn't use fusion and thus its lifespan is more in line with the creationist worldview and I responded with neutrinos emitted from the fusion reactions in the sun.
