Terrible Ofsted - teachers, please help!

[TeenageWildlife]

DS in year 11. the school has received a terrible Ofsted - mostly 4's. A new head came in a year ago and failed to improve the school.They are particularly failing in English and Maths and say my DS's year is already too far behind.
I was concerned already, this is not a surprise, have been trying to motivate and help from this end for ages.
My question is, what on earth can I do/ask the school to do? I don't know where to start.

Ofsted will have given them targets to meet.

Your DS is in Y11, and so has around 7 months left there. I'd concentrate on him, what GCSEs is he taking and what can you do to ensure he has the best chance possible. Websites, past papers, revision guides and independent study.Is he staying on for 6th form, or moving to a college?

School will be given specific targets to meet, and another OFSTED fairly quickly to check how they are doing. They will be getting specialist advice and support from other, successful schools to target their weaknesses.
What was the last OFSTED like?

How is your DS doing himself? Is he reaching the required grade to do whatever he want next year?

Could you consider a tutor to support him maybe?

Chase coursework. Hard. Make sure he is at least achieving, preferably exceeding his target grade. Talk to his teachers to make sure that is happening now, and if he isn't where he should be, get them to make arrangements to help him improve (if possible).

Ask if they are doing extra revision classes (I always do this for at least a month before exams). Make sure you know where to find past papers and mark schemes, but pace yourself with them.

Get revision guides and make sure he starts his revision early (that is for you and DS, rather than the school).

I really appreciate these responses. I have always bought revision guides and past papers and force gently encourage him to work as much as possible.
I am considering a tutor in English and Maths simply for him to catch up but they are hard to come by around here. I have helped him as much as I can with English - taking him to the theatre discussing his books etc. and he has done maths modules and done okay in those - again with revision help from me.
I have been badgering teachers to help him and help me to help him (they must be sick of me) as I was aware of the problem. DD in different school and I never badgered a single teacher as happy with the school.
I think I would like to email the school and staff concerned and ask for help, but I am not sure what to do.
Sixth form wise, he is not an independent learniner so college out, and not really a choice of other school so he would have to stay there

Does his school have a login for mymaths.co.uk? They've got lessons and interactive questions covering everything on his GCSE.

Yes. I will try and encourage him to go on there.