Under what circumstances would it matter? As long as people believe the earth is older than around 3,000 years they are going to have more of a problem with general background ignorance than their misconceptions about that specific fact.
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.
