He's only 16 and won't be 17 till next year so he's a year ahead of himself really.

He's going to see his yr advisor tomorrow and talk to her but he's got loads of questions I can't answer at the moment as I've no idea how the school system works over here!!
He really needs to be talking with the careers advisor as well. The year advisor really works with welfare based issues and while they can be good for guidence, the careers advisor (or transition advisor if he goes to a catholic school) is the person he needs to be talking to regarding subject selections and how this will help with getting into courses. That's what their job is.
If you have any questions, PM me ( i work in the area so can help you out a bit )