@JHS and @PurpleTitan thank you both. Sounds like it might be a good idea to have a conversation with his school counsellor earlier rather than later. DS tells me a number of students he knows in his program have aspirations to study in the US and are already doing SAT prep so it maybe that applying to US schools is something that the school counsellors are going to get some experience with. Any advice on when would be best to write the SAT/ACT (or both)?