The Church still encourages dioceses and religious communities to have high school seminaries. Therefore, the Church thinks that someone can discern when they are under 18. We have many saints who discerned young.
Do most American seminarians discern at such a young age today? No, but I don’t see why that means some can’t. I also see that a diocese may not see the dedication of personel and money to such an endevour as the best use of reasources and not have high school seminaries. Each diocesean bishop and vocation director need to do what they think is best to promote vocations, and unless it is outright heresy or completely farsical, I don’t have the information to make a judgement.
Some dioceses and communities support minor seminaries, and unless we want to put ourselves above the Church’s judgement, we shouldn’t judge them either.
This is one option for discernent; staying at the parish is another. For some one is better, for some the other. Without speaking with someone personally, I have no way to tell which is better for them.
I myself am a memebr of the only community that maintains two high school seminaries in the US. We accept anyone who has the proper dispostions to discern if their parents too support the formation independent of economics. (Both start at 7th grade but we very often receive teenagers for 9th or 10th grade.)
One school is in New Hampshire:
mylegionaries.org/articulo.phtml?se=377&ca=756&te=475&id=29843
The other in Indiana (near Chicago):
mylegionaries.org/articulo.phtml?se=377&ca=756&te=475&id=29846
So neither are near Atlanta, unfortunately.
I was a member of the Community in Indiana 2 years while doing travelling ministry; and can tell you that it is a positive environment for teenagers discerning.
(Obviously, whether in a high school seminary or at hope, anyone discerning should be active in the local Church; I would take that as a given.)