How late is too late to apply to sixth form?

Hi! Im in year 11 and I'm planning to take English Lit, Politics and Econ to do Law at uni.
The issue is though, in my year 10 mocks I got a grade 6 in Maths and in order to do Econ at my dream sixth form I need a grade 8-9.
So my only chance to boost it up is during my year 11 PPEs in the first week November.
However I'm a bit concerned cause most of my classmates have already applied to sixth form and I feel that applying in December might be too late.
I have checked the application deadlines for my sixth form options and its until Jan so its not like I'd be really late but at the same time, the sixth forms Im applying to are really competitive (LAE stratford, NCS ect.) so its better to apply earlier, right?
I've also heard that the earlier you apply the more chance you get into getting in and applications might close sooner if there are too many so thats making me a bit stressed aswell.
But again I just might be making a fuss over nothing so it'd be really helpful if you guys could clarify and help me out :')

I don’t live in London so I don’t know much but some schools I know some people just showed up on results day and got in. And with predicted none of the schools I applied to cared much at all about my predicted only my real thing. I don’t think they’ll look at all the applicants until January so don’t worry.

Do more research on how they look at applications. For my sixth-form, they could only look at an application once they recieved the December mocks, so I could apply early and be confident that if I did well in December, I'd get a place. It might be the same or different for these sixth forms.

hii! as someone who goes to a competitive london sixth form (bma) it doesn’t make much of a difference when u apply (just make sure its before the deadline!) so it’ll be fine to apply in dec as from what ive seen, theyre not filling up spaces at this time. instead, what they are doing is checking ur mocks to keep you in their system for when u get ur actual gcse grades. hope this makes sense!

I think it defo depends on the sixth form like everyone’s saying, but one of my friends applied the night before y12 started and got in, some near me take applications for a week or so once the years started too so I wouldn’t worry too much!