>I think american born high schoolers shouldn't get the "'", until they are in college or beyond.<
Sounds reasonable, but you'd have to carve out an exception for those who compete for other countries in international competitions such as the World Youth Championships.
The other problem is that in most cases, those with dual citizenship ultimately choose to compete for other countries. It's almost always easier to make their teams. That being the case, there's an advantage (at least to statistically minded folks) to giving them the ' as soon as it is known that they have non-US citizenship (until they compete for the US or declare their intention of doing so.)