I have a similar scenario, DS very keen in Math, pretty much self learned through Khan academy; While in Grade 4 he was already doing Math with 8th graders. This year with Pandemic we moved him to public school (Grade 5) and also dual enrolled in a college for calculus. He is not happy doing place value and decimal addition in his school but enjoys his college as the learning pace is different.

Good point around the High school credits, I was under assumption it would be automatic, I guess the negotiations with school never stops.