Long story short, I’ve been homeschooled from 7th grade to now [9th grade]. But my family and I are moving to South Carolina sometime between spring and summer of ‘09, so I planned on going back into public school there.
I need to know how being homeschooled in one state, then moving into another state and being enrolled in public school worked, as far as high school credits go?

Depends even going from one hs to another can mean different credits. My friend transfered and lost all her credits. When you go there you register, you might have to take a test (most likely) to see if you can even be in that grade. If you don’t meet the requirements to be in 9th grade then theyll hold you back. It just depends on the school i suppose. That’s all i know sorry. oh and good luck with moving, i moved to it was hard at first but it got easy. I have some friends who were home schooled and moved to public and they made friends fast.
if u were in the IB program this wouldn’t even be an issue
Well, I have a friend who did the same thing and it was complicated for him.
Contact the counselor at the school you plan to attend for accurate info. Because it is high school, it’s not likely that they’ll put you in a grade that is higher or lower than the one you “belong” in based on your age. But what courses you receive credit for, and what you still have to take, will depend on what you know, and they may measure THAT with some placement tests. For example, if you’re from another state, you may not have taken South Carolina history, and that may be required.
Chances are excellent that you will be in good shape academically. South Carolina is very friendly, so go in with an open mind and you will make friends fast. Best of luck.