Welcome! I also replied to your other thread. Check your state DOE or higher ed website for dual/concurrent enrollment info. Also, he may or may not have to apply as a transfer student, depending on how many college credits he will have accumulated by then, and whether he was matriculated at the time he took them. If he does apply as a transfer student, the high school transcript and recognitions will be much less important than his college transcript.
As it happens, very few colleges actually require a high school diploma in order to be admitted. They require certain courses (which will be listed on the college or state higher ed site). This has been the case for quite a long time. No one in my FOO has a high school diploma, and all of us have multiple graduate degrees, mostly terminal.
