A-level Statistics v MathsWatch this thread
Also right now it's only November so no matter what grade he is on, I'd still say its possible for him to get the 7 he needs to move up a grade. I'd recommend for him to check out Maths Genie. I used it when I did GCSE Maths and it's very good. all topics are laid out clearly by Grade, and have videos for revision and exam questions to do.
If he tries his best then I have no doubt he'll be able to achieve the grade 7 he needs to do A Level Maths.
What other A levels is he considering with it?