I guess I'm not sure I totally understand your concern Wren. HG kids as a general rule do very well on standardizes tests such as state tests or SAT or ACT. Many are able to score at the level of a strong college applicant on the SAT or ACT without any preparation by the time they are in sixth or seventh grade. That isn't to say that everything about homeschooling is a breeze, but as a rule pretty much the last thing you have worry about is whether or not they will pass standardized tests or be able to get into college.

I think maybe you are asking what happens if a student wants to radically accelerate and they are homeschooled. If that's the question, there is quite a lot of flexibility in that. Parents typically design the course of study and prepare the transcript for college admissions. Homeschooled parents don't have to ask permission or negotiate grade skips, your kid can just work on the level he or she is prepared to work on. Many students take part time college classes when they are ready and may enter full time when it seems most desirable for the family weighing a variety of factors (academic, financial, social, etc.) That may or may not be at the typical chronological age. Our child entered college a few years early and it was no problem.