It’s called dual credit. My kid did it. You can take college courses that count as high school courses too. Mine hadn’t racked up enough credits to graduate with a BA by the end of HS (in our area they limit you to 15 per term for 3 years...so technically you could), nor did he do the extra curricula stuff this kid did. But he did finish 12th grade with his HS diploma and an AA (78 transferable hours) so he was able to graduate college with a BA at 19. This kid’s feat was phenomenal in that he did both plus extra curricula. My kid opted out of the HS part and you’ll find plenty of kids doing the same these days. I think I know at least a dozen kids who graduated this year with their HS diploma and an AA. And to answer your question, you get your HS diploma and then they award you the BA or AA right after that. You get into college by testing in, you usually have to score a certain level on the college level placement test (in our area, you have to be able to test into College Alg, and Comp I.)
Did the government high school get to collect your son’s allotment to the school while he was attending community college?
Congratulations to you and your son.
My son took a bunch of AP classes. He was so well versed in the topics that he often taught the sessions during the school day and tutored in the evening. He and the students he tutored achieved the top score of "5" on their AP tests. He had enough credits to be a college sophomore the day he graduated from high school. He should have taken those AP credits to the local college to convert them to college credits before he went to USMC boot camp. It would have been an immediate promotion to PFC.