GSCE Rec as a US Parent, Teen Son

We are transitioning to the UK. I work remotely.

Our biggest concern in the transition are the GSCE's. We are aware the US school system is eons behind the UK standards, even if hebis in the AP tier in the US.

What are some recommendations, other than getting a tutor. Tips?

He wants to be Pre-Med and eventually become a Pediatrician.

I am aware he will need to take the A levels afterwards.

Thanks!