Like other homeschool parents, at one point right before she finished her coursework at the community college, I printed out her HS diploma and moved her on. Oh, I did do one smart thing, because she was still considered in high school at the time of enrollment, she didn't have to take ACT or SAT--by the time she went to a 4 year college, she was already established and considered a transfer student; therefore they didn't require any testing either. She has a great GPA and is extremely active. She is age 18 now and a Jr. in college.
My son is an 18 yo junior in college as well, but because of the sequencing of his courses he will be a senior for at least two years before he graduates. Of course, his situation does free him to take a lot of courses outside his major for fun to keep his number of credits up to full time.