US high school to UK

My son is 15, turning 16 this December. He's currently a freshman in a US high school.

We're trying to figure out his best course of action, whether that's to use online high school courses, or try to get him caught up to UK standards so he has the flexibility that comes with UK A levels to choose what he wants to specialize in.

Unfortunately this year has been tough on him. His dad passed away last year, and he's been struggling with going to class and isn't going to get many credits for this year.

His principal here also wants to know if credits transfer to the UK. I assume they don't.

If he does want to go the GCSE route, will they test him to see what level he's at, and place him accordingly?

'Credits' are not really a thing. You take GCSE tests at the end of sophomore (equivalent) year and you either pass the tests or not. And then you can either retake some and/ or start Higher education. Normally people take between 8 and 11 in various subjects. If you fail all your GCSEs, you can still move into higher education if you can prove you meet the entrance requirements of a course (they may make you retake some GCSEs or take an equivalence test).

My husband did not pass any GCSEs and he still got gainful employment (in fact, he makes more than I do with my three post-high school qualifications!).

The problem is that GCSEs are at least a two year course, meaning if he started UK schools next academic year, he would have missed half the content of his courses....